Aluminum substrates and lithographic printing plate precursors

ABSTRACT

An aluminum-containing substrate can be provided for use in lithographic printing plate precursors. Before radiation-sensitive layers are applied, a grained and sulfuric acid anodized aluminum-containing support is treated with an alkaline or acidic pore-widening solution to provide its outer surface with columnar pores. The diameter of the columnar pores at their outermost surface is at least 90% of the average diameter of the columnar pores. Directly on this treated surface, a hydrophilic layer is applied, which hydrophilic layer contains a non-crosslinked hydrophilic polymer having carboxylic acid side chains.

RELATED APPLICATION

Reference is made to copending and commonly assigned U.S. Ser. No.13/221,940, filed on Aug. 31, 2011 (now published as 2013/0052589), byHayashi.

FIELD OF THE INVENTION

This invention relates to the preparation of unique aluminum substratesand lithographic printing plate precursors containing the substrates.This invention also relates to methods for making the substrates andprecursors, and to methods for using them to prepare lithographicprinting plates.

BACKGROUND OF THE INVENTION

In conventional or “wet” lithographic printing, ink receptive regions,known as image areas, are generated on a hydrophilic surface. When thesurface is moistened with water and ink is applied, the hydrophilicregions retain the water and repel the ink, and the ink receptiveregions accept the ink and repel the water. The ink is transferred tothe surface of a material upon which the image is to be reproduced. Forexample, the ink can be first transferred to an intermediate blanketthat in turn is used to transfer the ink to the surface of the materialupon which the image is to be reproduced.

Imageable elements useful to prepare lithographic printing platestypically comprise one or more imageable layers applied over thehydrophilic surface of a substrate. The imageable layers include one ormore radiation-sensitive components that can be dispersed in a suitablebinder. Alternatively, the radiation-sensitive component can also be thebinder material. Following imaging, either the imaged regions or thenon-imaged regions of the imageable layer are removed by a suitabledeveloper, revealing the underlying hydrophilic surface of thesubstrate. If the imaged regions are removed, the element is consideredas positive-working. Conversely, if the non-imaged regions are removed,the element is considered as negative-working. In each instance, theregions of the imageable layer (that is, the image areas) that remainare ink-receptive, and the regions of the hydrophilic surface revealedby the developing process accept water and aqueous solutions, typicallya fountain solution, and repel ink.

Direct digital or thermal imaging has become increasingly important inthe printing industry because of their stability to ambient light. Theimageable elements for the preparation of lithographic printing plateshave been designed to be sensitive to heat or infrared radiation and canbe exposed using thermal heads of more usually, infrared laser diodesthat image in response to signals from a digital copy of the image in acomputer a platesetter. This “computer-to-plate” technology hasgenerally replaced the former technology where masking films were usedto image the elements.

These imaging techniques require the use of alkaline developers toremove exposed (positive-working) or non-exposed (negative-working)regions of the imaged layer(s). In some instances of positive-workinglithographic printing plate precursors that are designed for IR imaging,compositions comprising infrared radiation-sensitive absorbing compounds(such as IR dyes) inhibits and other dissolution inhibitors make thecoating insoluble in alkaline developers and soluble only in theIR-exposed regions.

Independently of the type of lithographic printing plate, lithographyhas generally been carried out using a metal substrate such as asubstrate comprising aluminum or an aluminum alloy of various metalliccompositions. The surface of the metal sheet is generally roughened bysurface graining in order to ensure good adhesion to a layer, usually animageable layer, that is disposed thereon and to improve water retentionin non-imaged regions during printing. Such aluminum-supported imageableelements are sometimes known in the art as precursors to planographicprinting plates or lithographic printing plates.

Various aluminum support materials and methods of preparing them aredescribed in U.S. Pat. No. 5,076,899 (Sakaki et al.) and U.S. Pat. No.5,518,589 (Matsura et al.).

In general, to prepare aluminum-containing substrates for lithographicprinting plate precursors, a continuous web of raw aluminum is generallytaken from unwind section through a degreasing section to remove oilsand debris from the aluminum web, alkali etching section, a firstrinsing section, a graining section that can include mechanical orelectrochemical graining, or both, a second rinsing section,post-graining acidic or alkali-etching section, a third rinsing section,an anodization section using a suitable acid (such as sulfuric acid) toprovide an anodic oxide coating, a fourth rinsing section, a“post-treatment” section, a final or fifth rinsing section, and a dryingsection, before either being rewound or passed on to coating stationsfor application of imageable layer formulations.

In the anodization section, the aluminum web is treated to form analuminum oxide layer on its surface so it will exhibit a high degree ofmechanical abrasion resistance necessary during the printing process.This aluminum oxide layer is already hydrophilic to some degree, whichis significant for having a high affinity for water and for repellingprinting ink. However, the oxide layer is so reactive that is caninteract with components of the imageable layer in the imageableelement. The aluminum oxide layer can partially or completely cover thealuminum substrate surface.

When sulfuric acid is used for providing the aluminum oxide layer, theresulting substrate can exhibit poorer adhesion to overlyingradiation-sensitive compositions than if the substrate had been anodizedusing phosphoric acid. It is believed that the difference in adhesioncan be caused by different anodic pore sizes created from the differentacids used in anodization. That is, sulfuric acid anodization mayproduce smaller pores in the oxide layer.

Japanese Published Application 11-65096 (Fujifilm) describes a methodfor providing photosensitive lithographic printing plate precursors inwhich an anodic oxide layer is formed on the aluminum support, whichanodic oxide pores have a diameter of 20 nm or less. A negative-workingphotosensitive layer is directly applied to this oxide layer.

U.S. Patent Application Publication 2002/0033108 (Akiyama et al.)describes the formation of oxide layers on aluminum supports to controlthe average size of the oxide pores in the range of from 6 nm to 40 nm.A water-receptive subbing layer can be applied over the oxide layer.

U.S. Pat. No. 7,078,153 (Hotta) describes a support having apredetermined vacancy ratio and micropores (vacancies) in its oxidesurface.

After anodization, the substrate is typically “post-treated” with asuitable polymer to permanently seal the oxide pores so that componentsin the radiation-sensitive imageable layer do not enter the pores, andto further improve the hydrophilicity of the substrate surface so itbetter repels lithographic ink during the printing operation.

Commonly used post-treatment processes can include the reaction aluminumoxide with poly(vinyl phosphoric acid), or a mixture of sodium phosphateand sodium fluoride, to form a crosslinked hydrophilic layer on thesubstrate. To determine if pore sealing has occurred, the substrate canbe dipped in an aqueous dye solution and rinsed. If little dye is seenon the substrate, the pores have been properly sealed.

It would be desirable to omit this post-treatment step of a sulfuricacid anodized aluminum-containing substrate that must be evaluated withan aqueous dye solution.

It is highly important to have good adhesion of the radiation-sensitiveimageable layer to the underlying substrate. But it is also necessary tohave rapid and complete removal of the exposed (positive-working) andnon-exposed (negative-working) regions during development. These twoimportant requirements often work against each other. It is verydifficult to satisfy both requirements, especially when development iscarrier out on-press where good adhesion of the remaining imaging layeris needed for it to survive thousands of printing impressions andcomplete removal of imageable layer should be accomplished within 50printing impressions.

There is a need to improve both of these requirements especially whenthe sulfuric acid anodized substrates are used for the lithographicprinting plate precursors that are on-press developable.

SUMMARY OF THE INVENTION

The present invention provides a substrate comprising a grained andsulfuric acid anodized aluminum-containing support, which support hasalso been treated with an alkaline or acidic pore-widening solution toprovide its outer surface with columnar pores so that the diameter ofthe columnar pores at their outermost surface is at least 90% of theaverage diameter of the columnar pores,

the substrate further comprising a hydrophilic layer disposed directlyon the grained, sulfuric acid anodized and treated aluminum-containingsupport, the hydrophilic layer comprising a non-crosslinked hydrophilicpolymer having carboxylic acid side chains.

This invention also provides a lithographic printing plate precursorcomprising a substrate of this invention and at least oneradiation-sensitive imageable layer disposed over the substrate, theradiation-sensitive imageable layer comprising a radiation absorber,

the substrate comprising a grained and sulfuric acid anodizedaluminum-containing support, which support has also been treated with analkaline or acidic pore-widening solution to provide its outer surfacewith columnar pores so that the diameter of the columnar pores at theiroutermost surface is at least 90% of the average diameter of thecolumnar pores,

the substrate further comprising a hydrophilic layer disposed directlyon the grained, sulfuric acid anodized and treated aluminum-containingsupport, the hydrophilic layer comprising a non-crosslinked hydrophilicpolymer having carboxylic acid side chains.

In addition, the present invention provides a method of preparing alithographic printing plate comprising:

imagewise exposing the lithographic printing plate precursor of thepresent invention (for example, as described above) to provide anexposed precursor having exposed and non-exposed regions in theradiation-sensitive imageable layer, and

processing the exposed precursor to remove either the non-exposedregions or the exposed regions to provide a lithographic printing plate.

For example, the lithographic printing plate precursor used in thismethod can be a positive-working lithographic printing plate precursor,and processing the exposed precursor can be carried out off-press toremove the exposed regions to provide a lithographic printing plateusing an alkaline processing solution.

Alternatively, the lithographic printing plate precursor used in thismethod is a negative-working lithographic printing plate precursor, andprocessing of the exposed precursor is carried out off-press using wateror an alkaline processing solution to remove the non-exposed regions toprovide a lithographic printing plate.

Further, a lithographic printing plate can be obtained by the method ofthis invention (for example, as described above) wherein thelithographic printing plate comprises a substrate having thereon eitherexposed portions or non-exposed portions of a radiation-sensitiveimageable layer,

the substrate comprising a grained and sulfuric acid anodizedaluminum-containing support, which support has also been treated with analkaline or acidic pore-widening solution to provide its outer surfacewith columnar pores so that the diameter of the columnar pores at theiroutermost surface is at least 90% of the average diameter of thecolumnar pores,

the substrate further comprising a hydrophilic layer disposed directlyon the grained, sulfuric acid anodized, and treated aluminum-containingsupport, the non-radiation sensitive hydrophilic layer comprising anon-crosslinked hydrophilic polymer having carboxylic acid side chains,the non-crosslinked hydrophilic polymer being present at a dry coverageof at least 0.001 g/m² and up to and including 0.4 g/m².

Further, this invention provides a method for preparing analuminum-containing article, comprising:

treating a grained and sulfuric acid anodized aluminum-containingsupport with an alkaline or acidic pore-widening solution to providecolumnar pores in the outer surface so that the diameter of the columnarpores at their outermost surface is at least 90% of the average diameterof the columnar pores, to provide a substrate, and

forming a hydrophilic layer directly on the substrate, the hydrophiliclayer comprising a non-crosslinked hydrophilic polymer having carboxylicacid side chains, the non-crosslinked hydrophilic polymer being appliedto a dry coverage of at least 0.001 g/m² and up to and including 0.4g/m².

This invention provides a number of advantages. The lithographicprinting plate precursors are prepared using grained and sulfuric acidanodized aluminum-containing substrate instead of the more costlyphosphoric acid anodization. Adhesion of the radiation sensitiveimageable layer to the sulfuric acid anodized substrate is improved,especially for on-press development so that thousands of impressions canbe printed. However, the appropriate portions of the radiation sensitiveimageable layer are quickly removed during development, for examplewithin a few printed impressions during on-press development. Thus,quick removal of imageable layer during development is possible alongwith on-press printing durability. In addition, the present inventionavoids the need for the typical post-treatment process in order to sealoxide pores, either before or after the pore widening operation.

These advantages have been achieved in the practice of this invention bythe pore widening operation described herein whereby the oxide pores arewidened before application of a radiation sensitive imageable layerformulation. After pore widening, the substrate is coated with arelatively thin hydrophilic layer (that can be non-radiation sensitive)comprising a particular type of polymer having carboxylic acid sidechains.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Unless the context indicates otherwise, when used herein, the terms“substrate”, “lithographic printing plate precursor”, “positive-workinglithographic printing plate precursor”, and “negative-workinglithographic printing plate precursor” are meant to be references toembodiments of the present invention.

The term “support” is used herein to refer to an aluminum-containingmaterial (web, sheet, foil, or other form) that is then treated toprepare a “substrate” that refers to the hydrophilic article upon whichvarious layers are coated.

The term “post-treatment” refers to treating the grained and anodizedaluminum-containing support with an aqueous solution to coat it with aninterlayer on the anodized substrate. Such a “post-treatment” is notused in the practice of the present invention between the process ofpore widening and the application of the hydrophilic layer.

In addition, unless the context indicates otherwise, the variouscomponents described herein such as the components of the various layersin the imageable elements or of the pore-widening solutions used in themethod of this invention, refer to one or more of those components.Thus, the singular form “a”, “an”, or “the” is not necessarily meant torefer to only a single component but can also include the pluralreferents.

Terms that are not explicitly defined in the present application are tobe understood to have meaning that is commonly accepted by those skilledin the art. If the construction of a term would render it meaningless oressentially meaningless in this context, the term's definition should betaken from a standard dictionary.

Unless otherwise indicated, percentages refer to percents by dry weightof a composition or layer, or % solids of a solution.

As used herein, the term “radiation absorber” refers to compounds thatare sensitive to certain wavelengths of radiation and can convertphotons into heat within the layer in which they are disposed.

As used herein, the term “infrared” refers to radiation having a of atleast 700 nm and higher. In most instances, the term “infrared” is usedto refer to the “near-infrared” region of the electromagnetic spectrumthat is defined herein to be at least 700 nm and up to and including1400 nm.

For clarification of definitions for any terms relating to polymers,reference should be made to “Glossary of Basic Terms in Polymer Science”as published by the International Union of Pure and Applied Chemistry(“IUPAC”), Pure Appl. Chem. 68, 2287-2311 (1996). However, anydefinitions explicitly set forth herein should be regarded ascontrolling.

Unless otherwise indicated, the terms “polymer” and “polymeric” refer tohigh and low molecular weight polymers including oligomers and includeshomopolymers and copolymers.

The term “copolymer” refers to polymers that are derived from two ormore different monomers, in random order along the polymer backbone.That is, they comprise recurring units having different chemicalstructures.

The term “backbone” refers to the chain of atoms in a polymer to which aplurality of pendant groups can be attached. An example of such abackbone is an “all carbon” backbone obtained from the polymerization ofone or more ethylenically unsaturated polymerizable monomers. However,other backbones can include heteroatoms wherein the polymer is formed bya condensation reaction or some other means.

Uses

The substrates of this invention can be used to prepare lithographicprinting plate precursors as described in more detail below. Thesubstrates can be used for any application requiring hydrophilicaluminum-containing surfaces.

Substrate

The substrates prepared according to this invention are generallyprovided initially as a grained and sulfuric acid anodizedaluminum-containing support, that is, wherein aluminum as thepredominant component. Thus, the grained and sulfuric acid anodizedsupport can be composed of pure aluminum, aluminum alloys having smallamounts (up to 10% by weight) of other elements such as manganese,silicon, iron, titanium, copper, magnesium, chromium, zinc, bismuth,nickel, or zirconium, or be polymeric films or papers on which a purealuminum or aluminum alloy sheet is laminated or deposited (for example,a laminate of an aluminum sheet and a polyester film). Generally, thegrained pure aluminum or aluminum alloys are used in this invention. Thesupports can be in any useful form or shape including continuous webs,sheets, and coils.

The thickness of the resulting substrate can be varied but should besufficient to sustain the wear from printing and thin enough to wraparound a printing form. Generally, substrates have a thickness of atleast 100 μm and up to and including 600 μm.

In general, the supports used to prepare the substrates have the desiredtensile strength, elasticity, crystallinity, conductivity, and otherphysical properties that are conventional in the lithographic art, whichproperties can be achieved using known treatments such as heattreatment, cold or hot fabrication processes, or other methodsconventional in the art of aluminum alloy fabrication for lithographicsubstrate preparation.

The substrates can be prepared as continuous webs or coiled strips thatcan be cut into desired sheets at a later time.

The aluminum-containing surface of the support is generally cleaned,grained (for example electrochemically grained), and sulfuric acidanodized using suitable known procedures before the pore-wideningtreatment and application of hydrophilic layer according to thisinvention. For example, a degreasing treatment with a surfactant, anorganic solvent, or an alkaline water solution is typically used toremove oil and grease from the surface of the aluminum-containingsupport. Then, the surface can be roughened (or grained) using wellknown techniques, such as mechanical roughening, electrochemicalroughening, or a combination thereof (multi-graining). Electrochemicallygraining can be carried out in a suitable manner as described forexample in U.S. Pat. No. 7,049,048 (Hunter et al.).

In some embodiments, the surface of the aluminum-containing support canbe electrochemically grained using the procedure and chemistry describedin U.S. Patent Application Publication 2008/0003411 (Hunter et al.). Inthese procedures, the roughened aluminum-containing support is subjectedto alternating current preferably in an electrolytic solution containinga suitable strong acid such as hydrochloric, nitric acid, or mixturesthereof. The alternating current used in the graining process can haveany desired wave form that alternates between positive and negativevoltages including but not limited to, a square wave, trapezoidal wave,or sine wave. Such graining is carried out at a current density of atleast 50 A/dm² and up to and including 200 A/dm².

This electrochemically grained support can then be etched to remove atleast 100 mg of aluminum per m². Etching can be carried out by immersingthe metal sheet in a highly acidic solution or a highly alkalinesolution having a pH of at least 13 and a conductivity of from about 30mS/cm to about 90 mS/cm. It is desired to remove sufficient aluminummetal in order to change its optical density, which is directly relatedto the “smut” level on the surface of the aluminum sheet.

Such an electrochemically grained aluminum support can then be anodizedin an alternating current passing through a sulfuric acid solution(5-30%) at a temperature of at least 20° C. and up to and including 60°C. for at least 5 seconds and up to and including 250 seconds to form anoxide layer on the metal surface. Phosphoric acid is not used foranodization in the practice of this invention. Generally, sulfuric acidanodization is carried out to provide an aluminum oxide layer of atleast 0.3 g/m² and typically at least 1 g/m² and up to and including 10g/m², or up to and including 5 g/m². The conditions for sulfuric acidanodization are generally well known in the art, for example in U.S.Pat. No. 7,078,153 (Hotta) that is incorporated herein by reference.

This anodization treatment produces pores in the aluminum oxide layer.The vacancy of the aluminum oxide layer can vary from at least 20% andup to and including 70%, as defined by the equation:vacancy=(1−(density of oxide coating/3.98))×100

The formed aluminum oxide layer generally has fine concave parts thatare sometimes referred as “micropores” or “pores” that are distributed,perhaps uniformly, over the layer surface. The density (or vacancy) isgenerally controlled by properly selecting the conditions of thesulfuric acid anodization treatment. The pores can appear as columnswithin the aluminum oxide layer, as viewed in a cross-sectionalmicroimage. These columnar pores can have an average diameter of lessthan 20 nm before they are treated to widen the average diameter at theoutermost surface, or most of the columnar pores have an averagediameter of at least 5 nm and up to and including 20 nm before they aretreated.

According to this invention, the electrochemically grained and sulfuricacid anodized aluminum-containing support is then treated to widen thepores in the aluminum oxide layer (“pore-widening treatment”) so thatthe diameter of the columnar pores at their outermost surface (that is,nearest the outermost layer surface) is at least 90%, and more typicallyat least 92%, and even more than 100% of the average diameter of thecolumnar pores. The average diameter of the columnar pores can bemeasured using a field emission scanning electron microscope. Once thisaverage diameter is determined, it is possible to determine whether thediameter at the outermost surface is at least 90% of that averagediameter value using similar measuring techniques. Thus, while theprocess described in U.S. Patent Application Publication 2002/0033108(noted above) controls the average pore diameter, it fails to provide aprocess for controlling the pore diameter at the outermost pore surfaceso that it is at least 90% of the average pore diameter. Moreover, thepores are sealed according to the teaching in this publication usingknown methods including the use of an alkali metal silicate.

The columnar pores are widened using an alkaline or acidic pore-wideningsolution to remove at least 10 weight % and up to and including 80weight %, typically at least 10 weight % and up to and including 60weight %, or more likely at least 20 weight % and up to and including 50weight %, of the original aluminum oxide layer. Pore widening can thusbe accomplished using an alkaline solution containing sodium hydroxide,potassium hydroxide, lithium hydroxide, or mixtures of hydroxides,having a pH of at least 11 and up to and including 13, or more likelyhaving a pH of at least 11.5 and up to and including 12.5, and ahydroxide (such as a sodium hydroxide) concentration of at least 0.15g/l and up to and including 1.5 g/l. The alkaline or acidicpore-widening solution generally has conductivity of at least 0.8 mS/cmand up to and including 8.2 mS/cm.

Alternatively, an acidic solution containing an inorganic acid such assulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, ormixtures of these acids at a concentration of at least 10 g/l and up toand including 500 g/l or more likely of at least 20 g/l and up to andincluding 100 g/l.

Particularly useful pore-widening solutions comprise sodium hydroxide,potassium hydroxide, sulfuric acid, hydrochloric acid, nitric acid, orphosphoric acid.

The pore-widening treatment with the acidic or alkaline solution can becarried out by contacting the electrochemically grained and sulfuricacid anodized support, for example by immersion in the solution, for atleast 3 seconds and up to and including 300 seconds, and typically forat least 10 seconds and up to and including 120 seconds to providecolumnar pores having an average diameter of at least 20 nm and up toand including 40 nm. The treatment temperature is at least 0° C. and upto and including 110° C. or typically a treatment temperature of atleast 20° C. and up to and including 70° C.

Once the electrochemically grained and sulfuric acid anodizedaluminum-containing support has been treated with the pore-wideningsolution, a hydrophilic layer is formed over the resulting substrateusing a hydrophilic layer formulation that can contain appropriatecoating solvents. The method of this invention does not include theknown post-treatment processes using coatings of poly(vinyl phosphonicacid) or vinyl phosphonic acid copolymers, silicates, dextrin, calciumzirconium fluoride, or hexafluorosilicic acid, or treatments with aphosphate solution that also contains an inorganic fluoride (PF).

Rather, the hydrophilic layer applied to the substrate of this inventioncomprises one or more linear or branched, non-crosslinked hydrophilicpolymers, each polymer having carboxylic acid side chains (pendantgroups). In the present invention, these non-crosslinked hydrophilicpolymers are generally the only polymers present in this hydrophiliclayer, and they can be applied in an amount to provide a dry coverage ofat least 0.001 g/m² and up to and including 0.4 g/m², or more typicallyof at least 0.01 g/m² and up to and including 0.3 g/m². The acidic sidechains on the non-crosslinked hydrophilic polymer can be neutralized, orat least some of the side chains are neutralized (“partiallyneutralized”). In general, the non-crosslinked hydrophilic polymer hascarboxylic acid side chains that are neutralized to a degree of at least1 mol % and up to and including 60 mol %, based on the total moles ofcarboxylic acid side chains. More typically, the partial neutralizationof the side chains is at least 10 mol % and up to and including 50 mol%. Neutralization can be achieved by treating the polymer using ahydroxide or amine such as an alkaline metal hydroxide, alkaline earthmetal hydroxide, an inorganic amine, or an organic amine, and knownreaction conditions. In most embodiments, the hydrophilic layer isnon-radiation sensitive, meaning that it is not intentionally designedto absorb an amount of radiation of any wavelength so as to affectimaging or development effects in the practice of this invention.

One or more non-crosslinked hydrophilic polymers are present in thehydrophilic layer in an amount of at least 50 weight % and up to andincluding 100 weight %, or typically at least 70 weight % and up to andincluding 100 weight %, based on the total solids of the hydrophiliclayer.

The hydrophilic layer provided on the substrate is a “releasable layer”,meaning that at least 80 weight % (or typically at least 90 weight %) ofthe hydrophilic layer is removable after 150 impressions, or more likelyafter 500 impressions, using the following print test:

Test: Contacting the dry coated hydrophilic layer (0.22 g/m²) withFusion® G Magenta lithographic printing ink (DIC of Tokyo, Japan) and amixture of NA108W fountain solution (1 weight %, DIC of Tokyo, Japan)and isopropyl alcohol (1 weight %) as a fountain solution on aRoland-200® printing (Man-Roland, Germany) for at least 150 impressions.

Representative non-crosslinked hydrophilic polymers useful in thepractice of this invention include but are not limited to, homopolymersand copolymers comprising recurring units having at least partiallyneutralized carboxylic acid side chains. Such recurring units can bederived from ethylenically unsaturated polymerizable monomers such as(meth)acrylic acid, itaconic acid, maleic anhydride, maleic acid,(meth)acrylates having carboxy groups in the molecule, and others thatwould be readily apparent to one skilled in the art. Alternatively, apolymer containing alkyl ester side groups can be formed, and thesealkyl ester side groups can be reacted with an alkaline compound to formcarboxylic acid groups that can then be at least partially neutralized.

The non-crosslinked hydrophilic polymer can also have other recurringunits that do not contain carboxylic acid side groups, which recurringunits can be derived from one or more of poly(oxyethylene)(meth)acrylates, (meth)acrylamides, 2-(meth)acrylamido 2-methylpropanesulfonic acid and its salts, poly(oxyethylene) alkyl ether(meth)acrylate, vinyl phosphonic acid and its salts, acid phosphoxyethyl (meth)acrylate and its salts, acid phosphoxy propyl (meth)acrylateand its salts, acid phosphoxy polyoxyethylene glycol (meth)acrylate andits salts, acid phosphoxy polyoxypropylene glycol (meth)acrylate and itssalts, vinyl alcohol, vinyl pyrrolidone, vinyl imidazole, hydroxy ethyl(meth)acrylate, carboxylic acid ethyl (meth)acrylate, vinyl imidazole,vinyl caprolactam, and (3-acrylamidopropyl)trimethylammonium chloride.

The non-crosslinked hydrophilic polymers can also have recurring unitscomprising ethylenically unsaturated double bonds in side chains as longas such bonds are at levels that do not contribute to significantcrosslinking. Monomers that can be used to provide recurring units withsuch side chains are described for example in Japanese PublishedApplications JP 2001-312068 and JP 2005-14294.

The non-crosslinked hydrophilic copolymers useful in the presentinvention can be derived from two or more ethylenically unsaturatedpolymerizable monomers that are polymerized using known reactionconditions to provide the recurring units along the polymer chains inrandom order.

In such non-crosslinked hydrophilic copolymers, the recurring unitshaving carboxylic acid side groups (or neutralized carboxylic acid sidegroups) can comprise at least 1 mol % and up to and including 50 mol %of all recurring units, or typically at least 1 mol % and up to andincluding 30 mol % of all recurring units.

The hydrophilic polymers useful in this invention are non-crosslinked,meaning that crosslinked bonds or crosslinkable groups are not purposelyintroduced into the polymer chain or side groups. The non-crosslinkedhydrophilic polymers generally have a weight average molecular weight ofat least 1,000 and up to and including 200,000 as determined by GelPermeation Chromatography. They also generally have a glass transitiontemperature of at least 50° C. and up to and including 350° C. asmeasured using standard differential scanning calorimetry.

The hydrophilic layer can also comprise one or more inorganic phosphoricacids or inorganic phosphoric acid precursors. These compounds can bepresent in the hydrophilic layer in an amount of at least 0.1 weight %and up to and including 4 weight %, and typically in an amount of atleast 0.3 weight % and up to and including 3 weight %, based on thenon-crosslinked hydrophilic layer total solids. The term “inorganicphosphoric acid” is meant to include what is known as orthophosphoricacid (H₃PO₄) as well as inorganic polyphosphoric acids having theformula HO—(PO₂OH)_(x)H wherein x is the number of phosphoric acid unitsin the molecule. Such compounds can be an inorganic phosphoric acidprecursor that forms orthophosphoric acid upon hydrolysis. Other usefulinorganic phosphoric acid precursors include pyrophosphoric acid,metaphosphoric acid, and phosphoric anhydride.

The hydrophilic layer can be applied to and directly disposed on thealuminum-containing substrate using various techniques including coatingof the hydrophilic layer formulation by gravure roll coating, reverseroll coating, slot die coating, or spraying, or the substrate can beimmersed in the hydrophilic layer formulation for a suitable time.Solvents for the hydrophilic layer formulation include but are notlimited to, water, water-miscible alcohols, acetone, water-miscibleethers, and mixtures thereof. Water is the most useful solvent for thehydrophilic layer formulation.

In some embodiments, the hydrophilic layer formulation consistsessentially of one or more non-crosslinked hydrophilic polymers and oneor more inorganic phosphoric acids or inorganic phosphoric acidprecursors. This means that the no other components are essential to thehydrophilic polymer formulation. However, in other embodiments, optionaladditives of the hydrophilic formulation, and the resulting hydrophiliclayer can include one or more surfactants. In still other embodiments,the hydrophilic layer formulation consists essentially of the one ormore non-crosslinked hydrophilic polymers and optionally one or moresurfactants. As noted below, a positive-working or negative-workingradiation-sensitive imageable layer can be formed directly on thehydrophilic layer.

The backside (non-imaging side) of the substrate of this invention canbe coated with antistatic agents or slipping layers or a matte layer toimprove handling and “feel” of the imageable element.

Negative-Working Lithographic Printing Plate Precursors

Some embodiments of this invention can be formed by suitable applicationof a negative-working radiation-sensitive composition as described belowto a substrate of this invention to form a negative-working radiationsensitive imageable layer comprising a free radically polymerizablecompound, a radiation absorber (such as an infrared radiation absorber),and a compound to generate free radicals upon irradiation. There isgenerally only a single imageable layer comprising theradiation-sensitive composition and it can be the outermost layer in theelement. However, a topcoat can be present over the imageable layersthat are designed for off-press development.

Negative-working lithographic printing plate precursors are describedfor example, in EP Patent Publications 770,494A1 (Vermeersch et al.),924,570A1 (Fujimaki et al.), 1,063,103A1 (Uesugi), EP 1,182,033A1(Fujimako et al.), EP 1,342,568A1 (Vermeersch et al.), EP 1,449,650A1(Goto), and EP 1,614,539A1 (Vermeersch et al.), U.S. Pat. No. 4,511,645(Koike et al.), U.S. Pat. No. 6,027,857 (Teng), U.S. Pat. No. 6,309,792(Hauck et al.), U.S. Pat. No. 6,569,603 (Furukawa et al.), U.S. Pat. No.6,899,994 (Huang et al.), U.S. Pat. No. 7,045,271 (Tao et al.), U.S.Pat. No. 7,049,046 (Tao et al.), U.S. Pat. No. 7,261,998 (Hayashi etal.), U.S. Pat. No. 7,279,255 (Tao et al.), U.S. Pat. No. 7,285,372(Baumann et al.), U.S. Pat. No. 7,291,438 (Sakurai et al.), U.S. Pat.No. 7,326,521 (Tao et al.), U.S. Pat. No. 7,332,253 (Tao et al.), U.S.Pat. No. 7,442,486 (Baumann et al.), U.S. Pat. No. 7,452,638 (Yu etal.), U.S. Pat. No. 7,524,614 (Tao et al.), U.S. Pat. No. 7,560,221(Timpe et al.), U.S. Pat. No. 7,574,959 (Baumann et al.), U.S. Pat. No.7,615,323 (Shrehmel et al.), and U.S. Pat. No. 7,672,241 (Munnelly etal.), and U.S. Patent Application Publications 2003/0064318 (Huang etal.), 2004/0265736 (Aoshima et al.), 2005/0266349 (Van Damme et al.),and 2006/0019200 (Vermeersch et al.), all of which are incorporatedherein by reference. Other negative-working compositions and elementsare described for example in U.S. Pat. No. 6,232,038 (Takasaki), U.S.Pat. No. 6,627,380 (Saito et al.), U.S. Pat. No. 6,514,657 (Sakurai etal.), U.S. Pat. No. 6,808,857 (Miyamoto et al.), and U.S. PatentPublication 2009/0092923 (Hayashi), all of which are incorporated hereinby reference. The radiation-sensitive compositions and imageable layersused in such precursors can generally include one or more polymericbinders that facilitate the developability of the imaged precursors.Such polymeric binders include but are not limited to, those that arenot generally crosslinkable and are usually film-forming in nature(dissolvable in coating solvent) but other polymeric binders can bepresent at least partially as discrete particles (not-agglomerated).Such polymers can be present as discrete particles having an averageparticle size of at least 10 and up to and including 500 nm, andtypically at least 100 and up to and including 450 nm, and that aregenerally distributed uniformly within that layer. The particulatepolymeric binders exist at room temperature as discrete particles, forexample in an aqueous dispersion. Such polymeric binders generally havea molecular weight (M_(n)) of at least 5,000 and typically at least20,000 and up to and including 100,000, or at least 30,000 and up to andincluding 80,000, as determined by Gel Permeation Chromatography.

For negative-working lithographic printing plate precursors that aredesigned for on-press development, useful particulate polymeric bindersgenerally include polymeric emulsions or dispersions of polymers havinghydrophobic backbones to which are directly or indirectly linked pendantpoly(alkylene oxide) side chains (for example at least 10 alkyleneglycol units), optionally cyano or phenyl side groups, or both types ofside chains or side groups, that are described for example in U.S. Pat.No. 6,582,882 (Pappas et al.), U.S. Pat. No. 6,899,994 (Huang et al.),U.S. Pat. No. 7,005,234 (Hoshi et al.), and U.S. Pat. No. 7,368,215(Munnelly et al.), and US Patent Application Publication 2005/0003285(Hayashi et al.), all of which are incorporated herein by reference.More specifically, such polymeric binders include but are not limitedto, graft copolymers having both hydrophobic and hydrophilic segments,block and graft copolymers having polyethylene oxide (PEO) segments,polymers having both pendant poly(alkylene oxide) segments and cyanogroups, in recurring units arranged in random fashion to form thepolymer backbone, and various hydrophilic polymeric binders that canhave various hydrophilic groups such as hydroxyl, carboxy, hydroxyethyl,hydroxypropyl, amino, aminoethyl, aminopropyl, carboxymethyl, sulfono,or other groups readily apparent to a worker skilled in the art.

Alternatively, the particulate polymeric binders can also have abackbone comprising multiple (at least two) urethane moieties. Suchpolymeric binders generally have a molecular weight (M_(n)) of at least2,000 and typically at least 100,000 and up to and including 500,000, orat least 100,000 and up to and including 300,000, as determined bydynamic light scattering.

Additional useful polymeric binders are particulatepoly(urethane-acrylic) hybrids that are distributed (usually uniformly)throughout the imageable layer. Each of these hybrids has a molecularweight of at least 50,000 and up to and including 500,000 and theparticles have an average particle size of at least 10 and up to andincluding 10,000 nm (typically at least 30 and up to and including 500nm or at least 30 and up to and including 150 nm). These hybrids can beeither “aromatic” or “aliphatic” in nature depending upon the specificreactants used in their manufacture. Blends of particles of two or morepoly(urethane-acrylic) hybrids can also be used. Somepoly(urethane-acrylic) hybrids are commercially available in dispersionsfrom Air Products and Chemicals, Inc. (Allentown, Pa.), for example, asthe Hybridur® 540, 560, 570, 580, 870, 878, 880 polymer dispersions ofpoly(urethane-acrylic) hybrid particles. These dispersions generallyinclude at least 30% solids of the poly(urethane-acrylic) hybridparticles in a suitable aqueous medium that can also include commercialsurfactants, anti-foaming agents, dispersing agents, anti-corrosiveagents, and optionally pigments and water-miscible organic solvents.

These polymeric binders are generally present in an amount of at least 5and up to and including 70 weight % of the radiation-sensitivecomposition.

Other useful polymeric binders can be homogenous, that is, film-forming,non-particulate, or dissolvable in the coating solvent. Such polymericbinders include but are not limited to, (meth)acrylic acid and acidester resins [such as (meth)acrylates], polyvinyl acetals, phenolicresins, polymers derived from styrene, N-substituted cyclic imides ormaleic anhydrides, such as those described in EP 1,182,033A1 (Fujimakiet al.) and U.S. Pat. No. 6,309,792 (Hauck et al.), U.S. Pat. No.6,352,812 (Shimazu et al.), U.S. Pat. No. 6,569,603 (Furukawa et al.),and U.S. Pat. No. 6,893,797 (Munnelly et al.), all of which areincorporated herein by reference. Also useful are the vinyl carbazolepolymers described in U.S. Pat. No. 7,175,949 (Tao et al.), and thepolymers having pendant vinyl groups as described in U.S. Pat. No.7,279,255 (Tao et al.), both patents being incorporated herein byreference. Useful are random copolymers derived from polyethylene glycolmethacrylate/acrylonitrile/styrene monomers in random fashion and inparticulate form, dissolved random copolymers derived from carboxyphenylmethacrylamide/acrylonitrile/-methacrylamide/N-phenyl maleimide, randomcopolymers derived from polyethylene glycolmethacrylate/acrylonitrile/vinyl carbazole/styrene/-methacrylic acid,random copolymers derived from N-phenylmaleimide/methacrylamide/methacrylic acid, random copolymers derivedfrom urethane-acrylic intermediate A (the reaction product of p-toluenesulfonyl isocyanate and hydroxylethylmethacrylate)/acrylonitrile/N-phenyl maleimide, and random copolymersderived from N-methoxymethyl methacrylamide/methacrylicacid/acrylonitrile/n-phenylmaleimide. By “random” copolymers, we meanthe conventional use of the term, that is, the structural units in thepolymer backbone that are derived from the monomers are arranged inrandom order as opposed to being block copolymers, although two or moreof the same structural units can be in a chain incidentally.

Thus, the polymeric binders can be selected from any alkaline solutionsoluble (or dispersible) polymer having an acid value of at least 20 andup to and including 400 (typically at least 30 and up to and including200). The following described polymeric binders are particularly usefulin the manner but this is not an exhaustive list:

I. Film-forming polymers formed by polymerization of a combination ormixture of (a) (meth)acrylonitrile, (b) poly(alkylene oxide) esters of(meth)acrylic acid, and optionally (c) (meth)acrylic acid,(meth)acrylate esters, styrene and its derivatives, and (meth)acrylamideas described for example in U.S. Pat. No. 7,326,521 (Tao et al.) that isincorporated herein by reference. Some particularly useful polymericbinders in this class are derived from one or more (meth)acrylic acids,(meth)acrylate esters, styrene and its derivatives, vinyl carbazoles,and poly(alkylene oxide) (meth)acrylates.

II. Film-forming polymers having pendant allyl ester groups as describedin U.S. Pat. No. 7,332,253 (Tao et al.) that is incorporated herein byreference. Such polymers can also include pendant cyano groups or haverecurring units derived from a variety of other monomers as described inCol. 8, line 31 to Col. 10, line 3 of the noted patent.

III. Film-forming polymers having all carbon backbones wherein at least40 and up to and including 100 mol % (and typically at least 40 and upto and including 50 mol %) of the carbon atoms forming the all carbonbackbones are tertiary carbon atoms, and the remaining carbon atoms inthe all carbon backbone being non-tertiary carbon atoms. By “tertiarycarbon”, we refer to a carbon atom in the all carbon backbone that hasthree valences filled with radicals or atoms other than a hydrogen atom(which fills the fourth valence). By “non-tertiary carbon”, we mean acarbon atom in the all carbon backbone that is a secondary carbon(having two valences filled with hydrogen atoms) or a quaternary carbon(having no hydrogen atoms attached). Typically, most of the non-tertiarycarbon atoms are secondary carbon atoms. One way to represent a tertiarycarbon atom in the all carbon backbone is with the following Structure(T-CARBON):

wherein T₂ is a group other than hydrogen provided that T₂ does notinclude an ethylenically unsaturated free radically reactive group (suchas a —C═C— group). In many embodiments, T₂ is a pendant group selectedfrom N-carbazole, aryl (defined similarly as for Ar below), halo, cyano,—C(═O)Ar, —C(═O)OR, —C(═O)OAr, —C(═O)NHR, and —C(═O)NHAr pendant groups,wherein R is hydrogen or an alkyl, cycloalkyl, halo, alkoxy, acyl, oracyloxy group, and Ar is an aryl group other than a styryl group. Thequaternary carbon atoms present in the all carbon backbone of thepolymeric binder can also have the same or different pendant groupsfilling two of the valences. For example, one or both valences can befilled with the same or different alkyl groups as defined above for R,or one valence can be filled with an alkyl group and another valence canbe filled with a N-carbazole, aryl other than a styryl group, halo,cyano, —C(═O)R, —C(═O)Ar, —C(═O)OR, —C(═O)OAr, —C(═O)NHR, or —C(═O)NHArpendant group, wherein R and Ar are as defined above. The pendant groupsattached to the tertiary and quaternary carbons in the all carbonbackbone can be the same or different and typically, they are different.It should also be understood that the pendant groups attached to thevarious tertiary carbon atoms can be the same throughout the polymericmolecule, or they can be different. For example, the tertiary carbonatoms can be derived from the same or different ethylenicallyunsaturated polymerizable monomers. Moreover, the quaternary carbonatoms throughout the polymeric molecule can have the same or differentpendant groups.

In some embodiments, the film-forming polymeric binder can berepresented by the following Structure:

that is defined in more details in U.S. Patent Application Publication2008-0280229 (Tao et al.) that is incorporated herein by reference.

Representative recurring units comprising tertiary carbon atoms can bederived from one or more ethylenically unsaturated polymerizablemonomers selected from vinyl carbazole, styrene and derivatives thereof(other than divinylbenzene and similar monomers that provide pendantcarbon-carbon polymerizable groups), acrylic acid, acrylonitrile,acrylamides, acrylates, and methyl vinyl ketone. As noted above, two ormore different recurring units can be used. Similarly, representativerecurring units with secondary or quaternary carbon atoms can be derivedfrom one or more ethylenically unsaturated polymerizable monomersselected from methacrylic acid, methacrylates, methacrylamides, andα-methylstyrene.

IV. Film-forming, polymeric binders that have one or more ethylenicallyunsaturated pendant groups (reactive vinyl groups) attached to thepolymer backbone. Such reactive groups are capable of undergoingpolymerizable or crosslinking in the presence of free radicals. Thependant groups can be directly attached to the polymer backbone with acarbon-carbon direct bond, or through a linking group that is notparticularly limited. The reactive vinyl groups can be substituted withat least one halogen atom, carboxy group, nitro group, cyano group,amide group, or alkyl, aryl, alkoxy, or aryloxy group, and particularlyone or more alkyl groups. In some embodiments, the reactive vinyl groupis attached to the polymer backbone through a phenylene group asdescribed, for example, in U.S. Pat. No. 6,569,603 (Furukawa et al.)that is incorporated herein by reference. Other useful polymeric bindershave vinyl groups in pendant groups that are described, for example inEP 1,182,033A1 (Fujimaki et al.) and U.S. Pat. No. 4,874,686 (Urabe etal.), U.S. Pat. No. 7,729,255 (Tao et al.), U.S. Pat. No. 6,916,595(Fujimaki et al.), and U.S. Pat. No. 7,041,416 (Wakata et al.) that areincorporated by reference, especially with respect to the generalformulae (1) through (3) noted in EP 1,182,033A1.

V. Film-forming polymeric binders can have pendant 1H-tetrazole groupsas described in U.S. Patent Application Publication 2009-0142695(Baumann et al.) that is incorporated herein by reference.

VI. Still other useful polymeric binders can be film-forming or exist asdiscrete particles and include but are not limited to, (meth)acrylicacid and acid ester resins [such as (meth)acrylates], polyvinyl acetals,phenolic resins, polymers derived from styrene, N-substituted cyclicimides or maleic anhydrides, such as those described in EP 1,182,033(noted above) and U.S. Pat. No. 6,309,792 (Hauck et al.), U.S. Pat. No.6,352,812 (Shimazu et al.), U.S. Pat. No. 6,569,603 (noted above), andU.S. Pat. No. 6,893,797 (Munnelly et al.). Also useful are the vinylcarbazole polymers described in U.S. Pat. No. 7,175,949 (Tao et al.).Other useful polymeric binders are particulate poly(urethane-acrylic)hybrids that are distributed (usually uniformly) throughout theimageable layer. Each of these hybrids has a molecular weight of atleast 50,000 and up to and including 500,000 and the particles have anaverage particle size of at least 10 and up to and including 10,000 nm(typically at least 30 and up to and including 500 nm).

The radiation-sensitive composition (and imageable layer) includes oneor more free radically polymerizable components, each of which containsone or more free radically polymerizable groups that can be polymerizedusing free radical initiation. For example, such free radicallypolymerizable components can contain one or more free radicalpolymerizable monomers or oligomers having one or more additionpolymerizable ethylenically unsaturated groups, crosslinkableethylenically unsaturated groups, ring-opening polymerizable groups,azido groups, aryldiazonium salt groups, aryldiazosulfonate groups, or acombination thereof. Similarly, crosslinkable polymers having such freeradically polymerizable groups can also be used. Oligomers orprepolymers, such as urethane acrylates and methacrylates, epoxideacrylates and methacrylates, polyester acrylates and methacrylates,polyether acrylates and methacrylates, and unsaturated polyester resinscan be used. In some embodiments, the free radically polymerizablecomponent comprises carboxyl groups.

Free radically polymerizable compounds include urea urethane(meth)acrylates or urethane (meth)acrylates having multiplepolymerizable groups. For example, a free radically polymerizablecomponent can be prepared by reacting DESMODUR® N100 aliphaticpolyisocyanate resin based on hexamethylene diisocyanate (Bayer Corp.,Milford, Conn.) with hydroxyethyl acrylate and pentaerythritoltriacrylate. Useful free radically polymerizable compounds include NKEster A-DPH (dipentaerythritol hexaacrylate) that is available from KowaAmerican, and Sartomer 399 (dipentaerythritol pentaacrylate), Sartomer355 (di-trimethylolpropane tetraacrylate), Sartomer 295 (pentaerythritoltetraacrylate), and Sartomer 415 [ethoxylated (20)trimethylolpropanetriacrylate] that are available from Sartomer Company, Inc.

Numerous other free radically polymerizable components are known tothose skilled in the art and are described in considerable literatureincluding Photoreactive Polymers: The Science and Technology of Resists,A Reiser, Wiley, New York, 1989, pp. 102-177, by B. M. Monroe inRadiation Curing: Science and Technology, S. P. Pappas, Ed., Plenum, NewYork, 1992, pp. 399-440, and in “Polymer Imaging” by A. B. Cohen and P.Walker, in Imaging Processes and Material, J. M. Sturge et al. (Eds.),Van Nostrand Reinhold, New York, 1989, pp. 226-262. For example, usefulfree radically polymerizable components are also described in EP1,182,033A1 (Fujimaki et al.), beginning with paragraph [0170], and inU.S. Pat. No. 6,309,792 (Hauck et al.), U.S. Pat. No. 6,569,603(Furukawa), and U.S. Pat. No. 6,893,797 (Munnelly et al.). Other usefulfree radically polymerizable components include those described in U.S.Patent Application Publication 2009/0142695 (Baumann et al.), whichradically polymerizable components include 1H-tetrazole groups.

In addition to, or in place of the free radically polymerizablecomponents described above, the radiation-sensitive composition caninclude polymeric materials that include side chains attached to thebackbone, which side chains include one or more free radicallypolymerizable groups (such as ethylenically unsaturated groups) that canbe polymerized (crosslinked) in response to free radicals produced bythe initiator composition (described below). There can be at least twoof these side chains per molecule. The free radically polymerizablegroups (or ethylenically unsaturated groups) can be part of aliphatic oraromatic acrylate side chains attached to the polymeric backbone.Generally, there are at least 2 and up to and including 20 such groupsper molecule.

Such free radically polymerizable polymers can also comprise hydrophilicgroups including but not limited to, carboxy, sulfo, or phospho groups,either attached directly to the backbone or attached as part of sidechains other than the free radically polymerizable side chains.

This radiation-sensitive composition also includes an initiatorcomposition that includes one or more initiators that are capable ofgenerating free radicals sufficient to initiate polymerization of allthe various free radically polymerizable components upon exposure of thecomposition to imaging infrared radiation. The initiator composition isgenerally responsive, for example, to electromagnetic radiation in theinfrared spectral regions, corresponding to the broad spectral range ofat least 700 nm and up to and including 1400 nm, and typically radiationof at least 700 nm and up to and including 1250 nm. Alternatively, theinitiator composition can be responsive to exposing radiation in theviolet region of at least 250 and up to and including 450 nm andtypically at least 300 and up to and including 450 nm.

More typically, the initiator composition includes one or more anelectron acceptors and one or more co-initiators that are capable ofdonating electrons, hydrogen atoms, or a hydrocarbon radical.

In general, suitable initiator compositions for radiation-sensitivecompositions comprise initiators that include but are not limited to,aromatic sulfonylhalides, trihalogenomethylsulfones, imides (such asN-benzoyloxyphthalimide), diazosulfonates, 9,10-dihydroanthracenederivatives, N-aryl, S-aryl, or O-aryl polycarboxylic acids with atleast 2 carboxy groups of which at least one is bonded to the nitrogen,oxygen, or sulfur atom of the aryl moiety (such as aniline diatetic acidand derivatives thereof and other “co-initiators” described in U.S. Pat.No. 5,629,354 of West et al.), oxime ethers and oxime esters (such asthose derived from benzoin), α-hydroxy or α-amino-acetophenones,trihalogenomethyl-arylsulfones, benzoin ethers and esters, peroxides(such as benzoyl peroxide), hydroperoxides (such as cumylhydroperoxide), azo compounds (such as azo bis-isobutyronitrile),2,4,5-triarylimidazolyl dimers (also known as hexaarylbiimidazoles, or“HABI's”) as described for example in U.S. Pat. No. 4,565,769 (Dueber etal.), trihalomethyl substituted triazines, boron-containing compounds(such as tetraarylborates and alkyltriarylborates) and organoboratesalts such as those described in U.S. Pat. No. 6,562,543 (Ogata et al.),and onium salts (such as ammonium salts, diaryliodonium salts,triarylsulfonium salts, aryldiazonium salts, and N-alkoxypyridiniumsalts).

Hexaarylbiimidazoles, onium compounds, and thiol compounds as well asmixtures of two or more thereof are desired co-initiators or freeradical generators, and especially hexaarylbiimidazoles and mixturesthereof with thiol compounds are useful. Suitable hexaarylbiimidazolesare also described in U.S. Pat. No. 4,565,769 (Dueber et al.) and U.S.Pat. No. 3,445,232 (Shirey) and can be prepared according to knownmethods, such as the oxidative dimerization of triarylimidazoles.

Useful initiator compositions for IR radiation-sensitive compositionsinclude onium compounds including ammonium, sulfonium, iodonium, andphosphonium compounds, particularly in combination with cyanine infraredradiation-sensitive dyes. Useful iodonium cations are well known in theart including but not limited to, U.S. Patent Application Publication2002/0068241 (Oohashi et al.), WO 2004/101280 (Munnelly et al.), andU.S. Pat. No. 5,086,086 (Brown-Wensley et al.), U.S. Pat. No. 5,965,319(Kobayashi), and U.S. Pat. No. 6,051,366 (Baumann et al.). For example,a useful iodonium cation includes a positively charged iodonium,(4-methylphenyl)[4-(2-methylpropyl)phenyl]-moiety and a suitablenegatively charged counterion.

Thus, the iodonium cations can be supplied as part of one or moreiodonium salts, and the iodonium cations can be supplied as iodoniumborates also containing suitable boron-containing anions particularly incombination with cyanine infrared radiation-sensitive dyes. For example,the iodonium cations and the boron-containing anions can be supplied aspart of substituted or unsubstituted diaryliodonium salts that arecombinations of Structures (I) and (II) described in Cols. 6-8 of U.S.Pat. No. 7,524,614 (Tao et al.) that is incorporated herein byreference.

Useful IR radiation-sensitive initiator compositions can comprise one ormore diaryliodonium borate compounds. Representative iodonium boratecompounds useful in this invention include but are not limited to,4-octyloxyphenyl phenyliodonium tetraphenylborate,[4-[(2-hydroxytetradecyl)-oxy]phenyl]phenyliodonium tetraphenylborate,bis(4-t-butylphenypiodonium tetraphenylborate,4-methylphenyl-4′-hexylphenyliodonium tetraphenylborate,4-methylphenyl-4′-cyclohexylphenyliodonium tetraphenylborate,bis(t-butylphenyl)iodonium tetrakis(pentafluorophenyl)borate,4-hexylphenyl-phenyliodonium tetraphenylborate,4-methylphenyl-4′-cyclohexyl-phenyliodonium n-butyltriphenylborate,4-cyclohexylphenyl-phenyliodonium tetraphenylborate,2-methyl-4-t-butylphenyl-4′-methylphenyliodonium tetraphenylborate,4-methylphenyl-4′-pentylphenyliodoniumtetrakis[3,5-bis(trifluoromethyl)phenyl]borate,4-methoxyphenyl-4′-cyclohexyl-phenyliodoniumtetrakis(penta-fluorophenyl)borate,4-methylphenyl-4′-dodecylphenyliodonium tetrakis(4-fluorophenyl)borate,bis(dodecylphenyl)-iodonium tetrakis(pentafluorophenyl)-borate, andbis(4-t-butylphenyl)iodonium tetrakis(1-imidazolyl)borate. Usefulcompounds include bis(4-t-butylphenyl)-iodonium tetraphenylborate,4-methylphenyl-4′-hexylphenyliodonium tetraphenylborate,2-methyl-4-t-butylphenyl-4′-methylphenyliodonium tetraphenylborate, and4-methylphenyl-4′-cyclohexylphenyliodonium tetraphenylborate. Mixturesof two or more of these compounds can also be used in the initiatorcomposition.

The imageable layers comprise a radiation-sensitive imaging compositionthat includes one or more infrared radiation absorbers or one or more UVsensitizers. The total amount of one or more infrared radiationabsorbers or sensitizers is at least 1 and up to and including 30 weight%, or typically at least 5 and up to and including 20 weight %, based onthe imageable layer total solids.

In some embodiments, the radiation-sensitive composition contains a UVsensitizer where the free-radical generating compound is UV radiationsensitive (that is at least 150 nm and up to and including 475 nm),thereby facilitating photopolymerization. In some other embodiments, theradiation sensitive compositions are sensitized to “violet” radiation inthe range of at least 375 nm and up to and including 475 nm. Usefulsensitizers for such compositions include certain pyrilium andthiopyrilium dyes and 3-ketocoumarins. Some other useful sensitizers forsuch spectral sensitivity are described for example, in U.S. Pat. No.6,908,726 (Korionoff et al.) and WO 2004/074929 (Baumann et al.) thatdescribes useful bisoxazole derivatives and analogues, and U.S. PatentApplication Publications 2006/0063101 and 2006/0234155 (both Baumann etal.).

Still other useful sensitizers are the oligomeric or polymeric compoundshaving Structure (I) units defined in WO 2006/053689 (Strehmel et al.)that have a suitable aromatic or heteroaromatic unit that provides aconjugated n-system between two heteroatoms.

Additional useful “violet”-visible radiation sensitizers are thecompounds described in WO 2004/074929 (Baumann et al.). These compoundscomprise the same or different aromatic heterocyclic groups connectedwith a spacer moiety that comprises at least one carbon-carbon doublebond that is conjugated to the aromatic heterocyclic groups, and arerepresented in more detail by Formula (I) of the noted publication.

Other useful sensitizers for the violet region of sensitization are the2,4,5-triaryloxazole derivatives as described in WO 2004/074930 (Baumannet al.). These compounds can be used alone or with a co-initiator asdescribed above. Useful 2,4,5-triaryloxazole derivatives can berepresented by the Structure G-(Ar₁)₃ wherein Ar₁ is the same ordifferent, substituted or unsubstituted carbocyclic aryl group having 6to 12 carbon atoms in the ring, and G is a furan or oxazole ring, or theStructure G-(Ar₁)₂ wherein G is an oxadiazole ring. The Ar₁ groups canbe substituted with one or more halo, substituted or unsubstitutedalkyl, substituted or unsubstituted cycloalkyl, substituted orunsubstituted aryl, amino (primary, secondary, or tertiary), orsubstituted or unsubstituted alkoxy or aryloxy groups. Thus, the arylgroups can be substituted with one or more R′₁ through R′₃ groups,respectively, that are independently hydrogen or a substituted orunsubstituted alkyl group having from 1 to 20 carbon atoms (such asmethyl, ethyl, iso-propyl, n-hexyl, benzyl, and methoxymethyl groups)substituted or unsubstituted carbocyclic aryl group having 6 to 10carbon atoms in the ring (such as phenyl, naphthyl, 4-methoxyphenyl, and3-methylphenyl groups), substituted or unsubstituted cycloalkyl grouphaving 5 to 10 carbon atoms in the ring, a —N(R′₄)(R′₅) group, or a—OR′₆ group wherein R′₄ through R′₆ independently represent substitutedor unsubstituted alkyl or aryl groups as defined above. At least one ofR′₁ through R′₃ is an —N(R′₄)(R′₅) group wherein R′₄ and R′₅ are thesame or different alkyl groups. Useful substituents for each Ar₁ groupinclude the same or different primary, secondary, and tertiary amines.

Still another class of useful violet radiation sensitizers includescompounds represented by the Structure Ar₁-G-Ar₂ wherein Ar₁ and Ar₂ arethe same or different substituted or unsubstituted aryl groups having 6to 12 carbon atoms in the ring, or Ar₂ can be an arylene-G-Ar₁ orarylene-G-Ar₂ group, and G is a furan, oxazole, or oxadiazole ring. Anis the same as defined above, and Ar₂ can be the same or different arylgroup as Ar₁. “Arylene” can be any of the aryl groups defined for Ar₁but with a hydrogen atom removed to render them divalent in nature.

Some useful infrared radiation absorbers are sensitive to both infraredradiation (typically of at least 700 and up to and including 1400 nm)and visible radiation (typically of at least 450 and up to and including700 nm). These compounds also have a tetraaryl pentadiene chromophore.Such chromophore generally includes a pentadiene linking group having 5carbon atoms in the chain, to which are attached two substituted orunsubstituted aryl groups at each end of the linking group. These arylgroups can be substituted with the same or different tertiary aminegroups. The pentadiene linking group can also be substituted with one ormore substituents in place of the hydrogen atoms, or two or morehydrogen atoms can be replaced with atoms to form a ring in the linkinggroup as long as there are alternative carbon-carbon single bonds andcarbon-carbon double bonds in the chain. Other details of such compoundsare provided in U.S. Pat. No. 7,429,445 (Munnelly et al.).

Other useful infrared radiation absorbers include but are not limitedto, azo dyes, squarilium dyes, croconate dyes, triarylamine dyes,thioazolium dyes, indolium dyes, oxonol dyes, oxaxolium dyes, cyaninedyes, merocyanine dyes, phthalocyanine dyes, indocyanine dyes,indotricarbocyanine dyes, oxatricarbocyanine dyes, thiocyanine dyes,thiatricarbocyanine dyes, cryptocyanine dyes, naphthalocyanine dyes,polyaniline dyes, polypyrrole dyes, polythiophene dyes,chalcogenopyryloarylidene and bi(chalcogenopyrylo) polymethine dyes,oxyindolizine dyes, pyrylium dyes, pyrazoline azo dyes, oxazine dyes,naphthoquinone dyes, anthraquinone dyes, quinoneimine dyes, methinedyes, arylmethine dyes, squarine dyes, oxazole dyes, croconine dyes,porphyrin dyes, and any substituted or ionic form of the preceding dyeclasses. Suitable dyes are also described in U.S. Pat. No. 5,208,135(Patel et al.), U.S. Pat. No. 6,153,356 (Urano et al.), U.S. Pat. No.6,264,920 (Achilefu et al.), U.S. Pat. No. 6,309,792 (Hauck et al.),U.S. Pat. No. 6,569,603 (noted above), U.S. Pat. No. 6,787,281 (Tao etal.), U.S. Pat. No. 7,135,271 (Kawaushi et al.), and EP 1,182,033A2(noted above). Infrared radiation absorbing N-alkylsulfate cyanine dyesare described for example in U.S. Pat. No. 7,018,775 (Tao). A generaldescription of one class of suitable cyanine dyes is shown by theformula in paragraph [0026] of WO 2004/101280 (Munnelly et al.).

In addition to low molecular weight IR-absorbing dyes having IR dyechromophores bonded to polymers can be used as well. Moreover, IR dyecations can be used as well, that is, the cation is the IR absorbingportion of the dye salt that ionically interacts with a polymercomprising carboxy, sulfa, phospho, or phosphono groups in the sidechains.

Near infrared absorbing cyanine dyes are also useful and are describedfor example in U.S. Pat. No. 6,309,792 (noted above), U.S. Pat. No.6,264,920 (Achilefu et al.), U.S. Pat. No. 6,153,356 (noted above), andU.S. Pat. No. 5,496,903 (Watanabe et al.). Suitable dyes can be formedusing conventional methods and starting materials or obtained fromvarious commercial sources including American Dye Source (Baie D'Urfe,Quebec, Canada) and FEW Chemicals (Germany). Other useful dyes for nearinfrared diode laser beams are described in U.S. Pat. No. 4,973,572(DeBoer).

Useful IR-radiation sensitive compositions are described, for example,in U.S. Pat. No. 7,452,638 (Yu et al.), and U.S. Patent ApplicationPublications 2008/0254387 (Yu et al.), 2008/0311520 (Yu et al.),2009/0263746 (Ray et al.), and 2010/0021844 (Yu et al.).

The imageable layer can also include a poly(alkylene glycol) or an etheror ester thereof that has a molecular weight of at least 200 and up toand including 4000. The imageable layer can further include a poly(vinylalcohol), a poly(vinyl pyrrolidone), poly(vinyl imidazole), or polyesterin an amount of up to and including 20 weight % based on the total dryweight of the imageable layer.

Additional additives to the imageable layer include color developers oracidic compounds. As color developers, we mean to include monomericphenolic compounds, organic acids or metal salts thereof, oxybenzoicacid esters, acid clays, and other compounds described for example inU.S. Patent Application Publication 2005/0170282 (Inno et al.). Theimageable layer can also include a variety of optional compoundsincluding but not limited to, dispersing agents, humectants, biocides,plasticizers, surfactants for coatability or other properties, viscositybuilders, pH adjusters, drying agents, defoamers, preservatives,antioxidants, development aids, rheology modifiers or combinationsthereof, or any other addenda commonly used in the lithographic art, inconventional amounts. The imageable layer also optionally includes aphosphate (meth)acrylate having a molecular weight generally greaterthan 250 as described in U.S. Pat. No. 7,429,445 (Munnelly et al.) thatis incorporated herein by reference.

The radiation-sensitive composition can be applied to the substrate as asolution or dispersion in a coating liquid using any suitable equipmentand procedure, such as spin coating, knife coating, gravure coating, diecoating, slot coating, bar coating, wire rod coating, roller coating, orextrusion hopper coating. The radiation-sensitive composition can alsobe applied by spraying onto a suitable support (such as an on-pressprinting cylinder). Typically, the radiation-sensitive composition isapplied and dried to form an imageable layer.

The precursor can have a water-soluble or water-dispersible overcoat(also sometimes known as an “oxygen impermeable topcoat” or “oxygenbarrier layer”) disposed over the imageable layer. The topcoat can bethe outermost layer. Such overcoat layers can comprise one or morewater-soluble poly(vinyl alcohol)s having a saponification degree of atleast 90% and generally have a dry coating weight of at least 0.1 and upto and including 2 g/m² in which the water-soluble poly(vinyl alcohol)scomprise at least 60% and up to and including 99% of the dry overcoatlayer weight.

The overcoat can further comprise a second water-soluble polymer that isnot a poly(vinyl alcohol) in an amount of from about 2 to about 38weight %, and such second water-soluble polymer can be a poly(vinylpyrrolidone), poly(ethyleneimine), poly(vinyl imidazole), poly(vinylcaprolactone), or a random copolymer derived from two or more of vinylpyrrolidone, ethyleneimine, vinyl caprolactone, and vinyl imidazole, andvinyl acetamide.

Alternatively, the overcoat can be formed predominantly using one ormore of polymeric binders such as poly(vinyl pyrrolidone),poly(ethyleneimine), poly(vinyl imidazole), and random copolymers fromtwo or more of vinyl pyrrolidone, ethyleneimine and vinyl imidazole, andmixtures of such polymers. The formulations can also include cationic,anionic, and non-ionic wetting agents or surfactants, flow improvers orthickeners, antifoamants, colorants, particles such as aluminum oxideand silicon dioxide, and biocides. Details about such addenda areprovided in WO 99/06890 (Pappas et al.) that is incorporated byreference. However, in some embodiments, a water-soluble orwater-dispersible overcoat is not desired or present in the precursorand the imageable layer is the outermost layer in the precursor.

Illustrative of such manufacturing methods is mixing the variouscomponents needed for a specific imaging chemistry in a suitable organicsolvent or mixtures thereof [such as methyl ethyl ketone (2-butanone),methanol, ethanol, 1-methoxy-2-propanol, iso-propyl alcohol, acetone,γ-butyrolactone, n-propanol, tetrahydrofuran, and others readily knownin the art, as well as mixtures thereof], applying the resultingsolution to a substrate, and removing the solvent(s) by evaporationunder suitable drying conditions. Some representative coating solventsand imageable layer formulations are described in the Invention Examplesbelow. After proper drying, the coating weight of the imageable layer isgenerally at least 0.1 and up to and including 5 g/m² or at least 0.5and up to and including 3.5 g/m².

Layers can also be present under the imageable layer to enhancedevelopability or to act as a thermal insulating layer.

Once the various layers have been applied and dried on the substrate ofthis invention, the negative-working lithographic printing plateprecursors can be enclosed in water-impermeable material thatsubstantially inhibits the transfer of moisture to and from the elementand “heat conditioned” as described in U.S. Pat. No. 7,175,969 (notedabove) that is incorporated herein by reference.

The lithographic printing plate precursors can be stored and transportedas stacks of precursors within suitable packaging and containers knownin the art.

Positive-Working Lithographic Printing Plate Precursors

Some of the lithographic printing plate precursors of the presentinvention are positive-working and include one or more layers disposedon the substrate of this invention.

Some embodiments of such positive-working lithographic printing plateprecursors comprise a single imageable surface layer while otherembodiments comprise an inner layer and an outer surface layer disposedon the inner layer.

The lithographic printing plate precursors can rely on an infraredradiation absorbing compound dispersed within one or more polymericbinders that, upon suitable irradiation, are soluble, dispersible, orremovable in processing solutions including alkaline developers. Thus,the imageable layer(s), upon irradiation, undergoes a change insolubility properties with respect to the processing solution in itsirradiated (exposed) regions.

For example, “single-layer” positive-working lithographic printing plateprecursors are described for example, in EP 1,543,046 (Timpe et al.), WO2004/081662 (Memetea et al.), U.S. Pat. No. 6,255,033 (Levanon et al.),U.S. Pat. No. 6,280,899 (Hoare et al.), U.S. Pat. No. 6,391,524 (Yateset al.), U.S. Pat. No. 6,485,890 (Hoare et al.), U.S. Pat. No. 6,558,869(Hearson et al.), U.S. Pat. No. 6,706,466 (Parsons et al.), U.S. Pat.No. 6,541,181 (Levanon et al.), U.S. Pat. No. 7,223,506 (Kitson et al.),U.S. Pat. No. 7,247,418 (Saraiya et al.), U.S. Pat. No. 7,270,930 (Haucket al.), U.S. Pat. No. 7,279,263 (Goodin), and U.S. Pat. No. 7,399,576(Levanon), EP 1,627,732 (Hatanaka et al.), and U.S. Published PatentApplications 2005/0214677 (Nagashima), 2004/0013965 (Memetea et al.),2005/0003296 (Memetea et al.), and 2005/0214678 (Nagashima).

The surface layer can contain one or more phenolic polymeric bindersthat are generally soluble in alkaline developers (defined below) afterthermal imaging. In most embodiments of the lithographic printing plateprecursors, these polymeric binders are present in an amount of at least10 weight % and typically from at least 20 and up to and including 80weight % of the total dry imageable layer weight. By “phenolic”, we meana hydroxyl-substituted phenyl group.

Useful phenolic polymers include but are not limited to, poly(vinylphenols) or derivatives thereof. They can also include pendant acidicgroups such as carboxylic (carboxy), sulfonic (sulfo), phosphonic(phosphono), or phosphoric acid groups that are incorporated into thepolymer molecule or pendant to the polymer backbone. Other usefuladditional phenolic polymers include but are not limited to, novolakresins, resole resins, poly(vinyl acetals) having pendant phenolicgroups, and mixtures of any of these resins (such as mixtures of one ormore novolak resins and one or more resole resins). Generally, suchresins have a number average molecular weight of at least 3,000 and upto and including 200,000, and typically at least 6,000 and up to andincluding 100,000, as determined using conventional procedures. Typicalnovolak resins include but are not limited to, phenol-formaldehyderesins, cresol-formaldehyde resins, phenol-cresol-formaldehyde resins,p-t-butylphenol-formaldehyde resins, and pyrogallol-acetone resins, suchas novolak resins prepared from reacting m-cresol or an m,p-cresolmixture with formaldehyde using conventional conditions. For example,some useful novolak resins include but are not limited to,xylenol-cresol resins, for example, SPN400, SPN420, SPN460, and VPN1100(that are available from AZ Electronics) and EP25D40G and EP25D50G(noted below for the Examples) that have higher molecular weights, suchas at least 4,000.

Other useful additional resins include polyvinyl compounds havingphenolic hydroxyl groups, include poly(hydroxystyrenes) and copolymerscontaining recurring units of a hydroxystyrene and polymers andcopolymers containing recurring units of substituted hydroxystyrenes.Also useful are branched poly(hydroxystyrenes) having multiple branchedhydroxystyrene recurring units derived from 4-hydroxystyrene asdescribed for example in U.S. Pat. No. 5,554,719 (Sounik) and U.S. Pat.No. 6,551,738 (Ohsawa et al.), and U.S. Published Patent Applications2003/0050191 (Bhatt et al.), 2005/0051053 (Wisnudel et al.), and2008/2008/0008956 (Levanon et al.). For example, such branchedhydroxystyrene polymers comprise recurring units derived from ahydroxystyrene, such as from 4-hydroxystyrene, which recurring units arefurther substituted with repeating hydroxystyrene units (such as4-hydroxystyrene units) positioned ortho to the hydroxy group. Thesebranched polymers can have a weight average molecular weight (M_(w)) ofat least 1,000 and up to and including 30,000. In addition, they canhave a polydispersity of less than 2. The branched poly(hydroxystyrenes)can be homopolymers or copolymers with non-branched hydroxystyrenerecurring units.

Another group of useful polymeric binders are poly(vinyl phenol) andderivatives thereof. Such polymers are obtained generally bypolymerization of vinyl phenol monomers, that is, substituted orunsubstituted vinyl phenols. Some vinyl phenol copolymers are describedin EP 1,669,803A (Barclay et al.).

The positive-working lithographic printing plate precursor also includesone or more radiation absorbers in the surface imageable layer. Suchcompounds are sensitive to near-infrared or infrared radiation, forexample of at least 700 and up to and including 1400 nm and typically atleast 700 and up to and including 1200 nm. Examples of useful infraredradiation absorbers are described above.

The radiation absorbing compound (or sensitizer) can be present in theimageable layer in an amount generally of at least 0.5% and up to andincluding 30% and typically at least 3 and up to and including 20%,based on total solids. The particular amount needed for this purposewould be readily apparent to one skilled in the art, depending upon thespecific compound used to provide the desired chromophore.

In some embodiments, the infrared radiation absorber is present in thesingle surface imageable layer. Alternatively or additionally, theinfrared radiation absorbers are located in a separate layer that is inthermal contact with the single surface imageable layer. Thus, duringimaging, the action of the infrared radiation absorber can betransferred to the single surface imageable layer without the compoundoriginally being incorporated into it.

The single-layer surface imageable element can be prepared by applyingthe layer formulation to the substrate of this invention (including anyhydrophilic layers on an aluminum sheet or cylinder) using conventionalcoating or lamination methods. Thus, the formulations can be applied bydispersing or dissolving the desired ingredients in a suitable coatingsolvent, and the resulting formulations are sequentially orsimultaneously applied to the substrate of this invention using suitableequipment and procedures, such as spin coating, knife coating, gravurecoating, die coating, slot coating, bar coating, wire rod coating,roller coating, or extrusion hopper coating. The formulations can alsobe applied by spraying onto a suitable substrate.

The coating weight for the single surface imageable layer can be fromabout 0.5 to about 2.5 g/m² and typically from about 1 to about 2 g/m².

The selection of solvents used to coat the surface imageable layerformulation depends upon the nature of the polymeric materials and othercomponents in the formulations. Generally, the formulation is coated outof acetone, methyl ethyl ketone, or another ketone, tetrahydrofuran,1-methoxypropan-2-ol, 1-methoxy-2-propyl acetate, and mixtures thereofusing conditions and techniques well known in the art. The coated layercan be dried in a suitable manner.

Other positive-working lithographic printing plate precursors of thisinvention are multi-layer imageable elements comprise a substrate ofthis invention, an inner layer (also known in the art as an“underlayer”), and an outer surface layer (also known in the art as a“top layer” or “topcoat”) disposed over the inner layer. Before thermalimaging, the outer layer is generally not soluble or removable by analkaline developer within the usual time allotted for development, butafter thermal imaging, the exposed regions of the outer surface layerare soluble in the alkaline developer. The inner layer is also generallyremovable by the alkaline developer. An infrared radiation absorber(described above) can also be present in such imageable elements, and istypically present in the inner layer but can optionally be in a separatelayer between the inner and outer layers. Useful IR radiation absorbersare described above.

Thermally imageable, multi-layer lithographic printing plate precursorsare described, for example, in U.S. Pat. No. 6,294,311 (Shimazu et al.),U.S. Pat. No. 6,352,812 (Shimazu et al.), U.S. Pat. No. 6,593,055(Shimazu et al.), U.S. Pat. No. 6,352,811 (Patel et al.), U.S. Pat. No.6,358,669 (Savariar-Hauck et al.), U.S. Pat. No. 6,528,228(Savariar-Hauck et al.), U.S. Pat. No. 7,163,770 (Saraiya et al.), U.S.Pat. No. 7,163,777 (Ray et al.), U.S. Pat. No. 7,186,482 (Kitson etal.), U.S. Pat. No. 7,223,506 (noted above), U.S. Pat. No. 7,229,744(Patel), U.S. Pat. No. 7,241,556 (Saraiya et al.), U.S. Pat. No.7,247,418 (noted above), U.S. Pat. No. 7,291,440 (Ray et al.), U.S. Pat.No. 7,300,726 (Patel et al.), and U.S. Pat. No. 7,338,745 (Ray et al.),U.S. Patent Application Publications 2004/0067432 A1 (Kitson et al.) and2005/0037280 (Loccufier et al.).

These multi-layer lithographic printing plate precursors are formed bysuitable application of an inner layer composition onto a suitablesubstrate of this invention.

The inner layer is disposed between the outer surface layer and thesubstrate of this invention. Typically, it is disposed directly on thesubstrate (including any hydrophilic coatings as described above). Theinner layer comprises a first polymeric binder that is removable by thelower pH processing solution of this invention and typically soluble inthat processing solution to reduce sludging. In addition, the firstpolymeric binder is usually insoluble in the solvent used to coat theouter surface layer so that the outer surface layer can be coated overthe inner layer without dissolving the inner layer. Mixtures of thesefirst polymeric binders can be used if desired in the inner layer. Suchpolymeric binders are generally present in the inner layer in an amountof at least 10 weight %, and generally at least 60 and up to andincluding 95 weight % of the total dry inner layer weight.

In most embodiments, the inner layer further comprises an infraredradiation absorber (as described above) that absorbs radiation of atleast 700 and up to and including 1400 and typically of at least 700 andup to and including 1200 nm. In most embodiments, the infrared radiationabsorber is present only in the inner layer. The infrared radiationabsorber can be present in the multi-layer lithographic printing plateprecursor in an amount of generally at least 0.5% and up to andincluding 30% and typically at least 3 and up to and including 25%,based on the total dry weight of the layer in which the compound islocated. The particular amount of a given compound to be used could bereadily determined by one skilled in the art.

The outer surface layer of the imageable element is disposed over theinner layer and in most embodiments there are no intermediate layersbetween the inner and outer surface layers. The outer surface layergenerally comprises a second polymeric binder that is usually differentthan the first polymeric binder described above for the inner layer.This second polymeric binder is a phenolic polymeric binder as describedabove for the single-layer lithographic printing plate precursor. Inmany embodiments, the outer surface layer is substantially free ofinfrared radiation absorbers, meaning that none of these compounds arepurposely incorporated therein and insubstantial amounts diffuse into itfrom other layers. However, in other embodiments, the infrared radiationabsorbing compound can be in both the outer surface and inner layers, asdescribed for example in EP 1,439,058A2 (Watanabe et al.) and EP1,738,901A1 (Lingier et al.), or in an intermediate layer as describedabove.

The outer surface layer can also include colorants as described forexample in U.S. Pat. No. 6,294,311 (noted above) includingtriarylmethane dyes such as ethyl violet, crystal violet, malachitegreen, brilliant green, Victoria blue B, Victoria blue R, and Victoriapure blue BO. These compounds can act as contrast dyes that distinguishthe non-exposed regions from the exposed regions in the developedimageable element. The outer surface layer can optionally also includecontrast dyes, printout dyes, coating surfactants, dispersing aids,humectants, biocides, viscosity builders, drying agents, defoamers,preservatives, and antioxidants.

The multi-layer lithographic printing plate precursors can be preparedby sequentially applying an inner layer formulation over the surface ofthe substrate of this invention, and then applying an outer layerformulation over the inner layer using conventional coating orlamination methods. It is important to avoid intermixing of the innerand outer surface layer formulations.

The inner and outer surface layers can be applied by dispersing ordissolving the desired ingredients in a suitable coating solvent, andthe resulting formulations are sequentially or simultaneously applied tothe substrate using suitable equipment and procedures, such as spincoating, knife coating, gravure coating, die coating, slot coating, barcoating, wire rod coating, roller coating, or extrusion hopper coating.The formulations can also be applied by spraying onto the substrate.

The selection of solvents used to coat both the inner and outer surfacelayers depends upon the nature of the first and second polymericbinders, other polymeric materials, and other components in theformulations. To prevent the inner and outer surface layer formulationsfrom mixing or the inner layer from dissolving when the outer surfacelayer formulation is applied, the outer surface layer formulation shouldbe coated from a solvent in which the first polymeric binder(s) of theinner layer are insoluble.

Generally, the inner layer formulation is coated out of a solventmixture of methyl ethyl ketone (MEK), 1-methoxy-2-propyl acetate (PMA),γ-butyrolactone (BLO), and water, a mixture of MEK, BLO, water, and1-methoxypropan-2-ol (also known as Dowanol® PM or PGME), a mixture ofdiethyl ketone (DEK), water, methyl lactate, and BLO, a mixture of DEK,water, and methyl lactate, or a mixture of methyl lactate, methanol, anddioxolane.

The outer surface layer formulation can be coated out of solvents orsolvent mixtures that do not dissolve the inner layer. Typical solventsfor this purpose include but are not limited to, butyl acetate,iso-butyl acetate, methyl iso-butyl ketone, DEK, 1-methoxy-2-propylacetate (PMA), iso-propyl alcohol, PGME and mixtures thereof.Particularly useful is a mixture of DEK and PMA, or a mixture of DEK,PMA, and isopropyl alcohol.

After drying the layers, the lithographic printing plate precursors canbe further “conditioned” with a heat treatment for at least 40 and up toand including 90° C. for at least 4 hours (for example, at least 20hours) under conditions that inhibit the removal of moisture from thedried layers. For example, the heat treatment is carried out for atleast 50 and up to and including 70° C. for at least 24 hours. Duringthe heat treatment, the lithographic printing plate precursors arewrapped or encased in a water-impermeable sheet material to represent aneffective barrier to moisture removal from the precursors, or the heattreatment of the precursors is carried out in an environment in whichrelative humidity is controlled to at least 25%. In addition, thewater-impermeable sheet material can be sealed around the edges of theprecursors, with the water-impermeable sheet material being a polymericfilm or metal foil that is sealed around the edges of the precursors.

In some embodiments, this heat treatment can be carried out with a stackcomprising at least 100 of the same lithographic printing plateprecursors, or when the precursor is in the form of a coil or web. Whenconditioned in a stack, the individual precursors can be separated bysuitable interleaving papers. The interleaving papers can be keptbetween the imageable elements after conditioning during packing,shipping, and use by the customer.

Imaging Conditions

During use, the lithographic printing plate precursor is exposed to asuitable source of exposing radiation depending upon the radiationabsorber present in the radiation-sensitive composition to providespecific sensitivity that is at a wavelength of at least 150 nm and upto and including 475 nm or infrared of at least 700 nm and up to andincluding 1400 nm. In some embodiments, imagewise exposure is carriedout using radiation the range of at least 350 nm and up to and including450 nm, or in the range of at least 700 nm and up to and including 1250nm.

For example, imaging can be carried out using imaging or exposingradiation from an infrared radiation-generating laser (or array of suchlasers). Imaging also can be carried out using imaging radiation atmultiple wavelengths at the same time if desired. The laser used toexpose the lithographic printing plate precursor is usually a diodelaser, because of the reliability and low maintenance of diode lasersystems, but other lasers such as gas or solid-state lasers can also beused. The combination of power, intensity and exposure time for laserimaging would be readily apparent to one skilled in the art.

The imaging apparatus can be configured as a flatbed recorder or as adrum recorder, with the lithographic printing plate precursor mounted tothe interior or exterior cylindrical surface of the drum. An example ofan useful imaging apparatus is available as models of Kodak® Trendsetterplatesetters available from Eastman Kodak Company that contain laserdiodes that emit near infrared radiation at a wavelength of about 830nm. Other suitable imaging sources include the Crescent 42T Platesetterthat operates at a wavelength of 1064 nm (available from GerberScientific, Chicago, Ill.) and the Screen PlateRite 4300, series or 8600series platesetter (available from Screen USA, Chicago, Ill.) thatoperates at a wavelength of 810 nm.

Imaging with infrared radiation can be carried out generally at imagingenergies of at least 30 mJ/cm² and up to and including 500 mJ/cm², andtypically at least 50 mJ/cm² and up to and including 300 mJ/cm²depending upon the sensitivity of the imageable layer. With theseplatesetters, any imaging parameters such as the “surface depth”parameter of a Magnus 800 platesetter (Eastman Kodak Company) or the“focus” parameter of a PlateRite 4300 platesetter (Dainippon ScreenCompany), are decided by observing the difference in contrast betweenexposed regions and non-exposed regions in a stepwise imaging process.By using such as stepwise imaged lithographic printing plate precursor,a shortened printing run is possible and the obtained prints are alsouseful for determining such imaging parameters.

Useful UV and “violet” imaging apparatus include Prosetter (fromHeidelberger Druckmaschinen, Germany), Luxel V-8 (from FUJI, Japan),Python (Highwater, UK), MakoNews, Mako 2, Mako 4 or Mako 8 (from ECRM,US), Micra (from Screen, Japan), Polaris and Advantage (from AGFA,Belgium), Laserjet (from Krause, Germany), and Andromeda® A750M (fromLithotech, Germany), imagesetters.

Imaging radiation in the UV to visible region of the spectrum, andparticularly the UV region (for example at least 150 nm and up to andincluding 475 nm), can be carried out generally using energies of atleast 0.01 mJ/cm² and up to and including 0.5 mJ/cm², and typically atleast 0.02 mJ/cm² and up to and including about 0.1 mJ/cm². It would bedesirable, for example, to image the UV/visible radiation-sensitiveimageable elements at a power density in the range of at least 0.5kW/cm² and up to and including 50 kW/cm² and typically of at least 5kW/cm² and up to and including 30 kW/cm², depending upon the source ofenergy (violet laser or excimer sources).

While laser imaging is desired in the practice of this invention,thermal imaging can be provided by any other means that provides thermalenergy in an imagewise fashion. For example, imaging can be accomplishedusing a thermoresistive head (thermal printing head) in what is known as“thermal printing”, described for example in U.S. Pat. No. 5,488,025(Martin et al.). Thermal print heads are commercially available (forexample, a Fujitsu Thermal Head FTP-040 MCS001 and TDK Thermal Head F415HH7-1089).

Development and Printing

After imaging, the imaged lithographic printing plate precursors can beprocessed “off-press” using a suitable processing solution describedherein, for example using water or an alkaline processing solution. Suchprocessing is carried out with imaged negative-working precursors for atime sufficient to remove the non-exposed regions of the imagedimageable layer to reveal the hydrophilic surface of the substrate ofthis invention, but not long enough to remove significant amounts of theexposed regions that have been hardened. The revealed hydrophilicsubstrate surface repels inks while the exposed regions accept ink.Thus, the non-exposed regions to be removed are “soluble” or “removable”in the processing solution because they are removed, dissolved, ordispersed within it more readily than the regions that are to remain.The term “soluble” also means “dispersible”. This processing can alsoremove the hydrophilic layer described above on the substrate in thenon-exposed regions.

When positive-working lithographic printing plate precursors are imagedand processed, the imaged (exposed) regions are removed duringprocessing while the non-exposed regions remain, revealing thehydrophilic substrate of this invention under the exposed regions.During such processing off-press, the hydrophilic layer described abovealso can be removed in the exposed regions.

Development off-press can be accomplished using what is known as“manual” development, “dip” development, or processing with an automaticdevelopment apparatus (processor). In the case of “manual” development,development is conducted by rubbing the entire imaged element with asponge or cotton pad sufficiently impregnated with a suitable developer(described below), and followed by rinsing with water. “Dip” developmentinvolves dipping the imaged element in a tank or tray containing theappropriate developer for at least 10 and up to and including 60 seconds(especially at least 20 and up to and including 40 seconds) underagitation, followed by rinsing with water with or without rubbing with asponge or cotton pad. The use of automatic development apparatus is wellknown and generally includes pumping a developer or processing solutioninto a developing tank or ejecting it from spray nozzles. The imagedprecursor is contacted with the developer in an appropriate manner. Theapparatus can also include a suitable rubbing mechanism (for example abrush or roller) and a suitable number of conveyance rollers. Somedeveloping apparatus include laser exposure means and the apparatus isdivided into an imaging section and a developing section.

Both aqueous alkaline developers and organic solvent-containingdevelopers or processing solutions can be used. Some useful developersolutions are described for example, in U.S. Pat. No. 7,507,526 (Milleret al.) and U.S. Pat. No. 7,316,894 (Miller et al.). Developer solutionscommonly include surfactants, chelating agents (such as salts ofethylenediaminetetraacetic acid), organic solvents (such as benzylalcohol), and alkaline components (such as inorganic metasilicates,organic metasilicates, hydroxides, and bicarbonates).

Useful alkaline aqueous developer solutions include 3000 Developer, 9000Developer, GOLDSTAR Developer, GREENSTAR Developer, ThermalProDeveloper, PROTHERM Developer, MX1813 Developer, and MX1710 Developer(all available from Eastman Kodak Company). These compositions alsogenerally include surfactants, chelating agents (such as salts ofethylenediaminetetraacetic acid), and alkaline components (such asinorganic metasilicates, organic metasilicates, hydroxides, andbicarbonates).

Organic solvent-containing developers are generally single-phaseprocessing solutions of one or more organic solvents that are misciblewith water. Useful organic solvents include the reaction products ofphenol with ethylene oxide and propylene oxide [such as ethylene glycolphenyl ether (phenoxyethanol)], benzyl alcohol, esters of ethyleneglycol and of propylene glycol with acids having 6 or less carbon atoms,and ethers of ethylene glycol, diethylene glycol, and of propyleneglycol with alkyl groups having 6 or less carbon atoms, such as2-ethylethanol and 2-butoxyethanol. The organic solvent(s) is generallypresent in an amount of from about 0.5 and up to 15% based on totaldeveloper weight. The organic solvent-containing developers can beneutral, alkaline, or slightly acidic in pH, and typically, they arealkaline in pH. Representative organic solvent-containing developersinclude ND-1 Developer, Developer 980, Developer 1080, 2 in 1 Developer,955 Developer, D29 Developer (described below), and 956 Developer (allavailable from Eastman Kodak Company).

The processing solution (or developer) can be applied to the imagedprecursor by rubbing, spraying, jetting, dipping, immersing, slot diecoating (for example see FIGS. 1 and 2 of U.S. Pat. No. 6,478,483 ofMaruyama et al.) or reverse roll coating (as described in FIG. 4 of U.S.Pat. No. 5,887,214 of Kurui et al.), or by wiping the outer layer withthe processing solution or contacting it with a roller, impregnated pad,or applicator. For example, the imaged precursor can be brushed with theprocessing solution, or it can be poured onto or applied by spraying theimaged surface with sufficient force to remove the non-exposed regionsusing a spray nozzle system as described for example in [0124] of EP1,788,431A2 (noted above) and U.S. Pat. No. 6,992,688 (Shimazu et al.).As noted above, the imaged precursor can be immersed in the processingsolution and rubbed by hand or with an apparatus. To assist in theremoval of the back side coating, a brush roller or other mechanicalcomponent can be placed in contact with the back side coating duringprocessing. Alternatively, the processing solution can be sprayed usinga spray bar using a sufficient force.

The processing solution can also be applied in a processing unit (orstation) in a suitable apparatus that has at least one roller forrubbing or brushing the imaged precursor while the processing solutionis applied. Residual processing solution can be removed (for example,using a squeegee or nip rollers) or left on the resulting lithographicprinting plate without any rinsing step. Excess processing solution canbe collected in a tank and used several times, and replenished ifnecessary from a reservoir. The processing solution replenisher can beof the same concentration as that used in processing, or be provided inconcentrated form and diluted with water at an appropriate time.

Following off-press development, the resulting lithographic printingplate can be postbaked with or without blanket or floodwise exposure toUV or visible radiation. Alternatively, a blanket UV or visibleradiation exposure can be carried out, without a postbake operation.

Printing can be carried out by putting the imaged and developedlithographic printing plate on a suitable printing press. Thelithographic printing plate is generally secured in the printing plateusing suitable clamps or other holding devices. Once the lithographicprinting plate is secured in the printing press, printing is carried outby applying a lithographic printing ink and fountain solution to theprinting surface of the lithographic printing plate. The fountainsolution is taken up by the surface of the hydrophilic substraterevealed by the imaging and processing steps, and the ink is taken up bythe remaining regions of the imageable layer. The ink is thentransferred to a suitable receiving material (such as cloth, paper,metal, glass, or plastic) to provide a desired impression of the imagethereon. If desired, an intermediate “blanket” roller can be used totransfer the ink from the lithographic printing plate to the receivingmaterial (for example, sheets of paper). The lithographic printingplates can be cleaned between impressions, if desired, usingconventional cleaning means.

For the imaged negative-working lithographic printing plate precursorsthat are designed for on-press development, the imaged lithographicprinting plate precursor is mounted on press wherein the non-exposedregions in the imageable layer are removed by a suitable fountainsolution, lithographic printing ink, or a combination of both, when theinitial printed impressions are made. Typical ingredients of aqueousfountain solutions include pH buffers, desensitizing agents, surfactantsand wetting agents, humectants, low boiling solvents, biocides,antifoaming agents, and sequestering agents. A representative example ofa fountain solution is Varn Litho Etch 142W+Varn PAR (alcohol sub)(available from Varn International, Addison, Ill.).

The fountain solution is taken up by the non-imaged regions, that is,the surface of the hydrophilic substrate of this invention revealed bythe imaging and development steps, and ink is taken up by the imaged(exposed) regions of the imaged layer. The ink is then transferred to asuitable receiving material (such as cloth, paper, metal, glass, orplastic) to provide a desired impression of the image thereon. Ifdesired, an intermediate “blanket” roller can be used to transfer theink from the imaged precursor to the receiving material. The imagedprecursors can be cleaned between impressions, if desired, usingconventional cleaning means.

The present invention provides at least the following embodiments andcombinations thereof, but other combinations of features are consideredto be within the present invention as a skilled artisan would appreciatefrom the teaching of this disclosure:

1. A substrate comprising a grained and sulfuric acid anodizedaluminum-containing support, which support has also been treated with analkaline or acidic pore-widening solution to provide its outer surfacewith columnar pores so that the diameter of the columnar pores at theiroutermost surface is at least 90% of the average diameter of thecolumnar pores,

the substrate further comprising a hydrophilic layer disposed directlyon the electrochemically grained, sulfuric acid anodized, and treatedaluminum-containing support, the hydrophilic layer comprising anon-crosslinked hydrophilic polymer having carboxylic acid side chains.

2. The substrate of embodiment 1 wherein the non-crosslinked hydrophilicpolymer is present at a dry coverage of at least 0.001 g/m² and up toand including 0.4 g/m².

3. The substrate of embodiment 1 or 2 wherein the non-crosslinkedhydrophilic polymer has partially neutralized carboxylic acid sidechains.

4. The substrate of any of embodiments 1 to 3 wherein thenon-crosslinked hydrophilic polymer has carboxylic acid side chains thatare neutralized to a degree of at least 1 mol % and up to and including60 mol %.

5. The substrate of any of embodiments 1 to 4 wherein the hydrophiliclayer is a releasable layer.

6. The substrate of any of embodiments 1 to 5 wherein the hydrophiliclayer is present at a dry coverage of at least 0.01 g/m² and up to andincluding 0.3 g/m².

7. The substrate of any of embodiments 1 to 6 wherein the hydrophiliclayer is a non-radiation-sensitive hydrophilic layer.

8. The substrate of any of embodiments 1 to 7 wherein the grained andsulfuric acid anodized and treated aluminum-containing support hascolumnar pores having an average diameter of at least 20 nm and up toand including 40 nm.

9. The substrate of any of embodiments 1 to 8 wherein at least 10 weight% and up to and including 80 weight % of the original aluminum oxidefrom sulfuric acid anodization has been removed by treatment with thealkaline or acidic pore-widening solution.

10. The substrate of any of embodiments 1 to 9 wherein the hydrophiliclayer further comprises an inorganic phosphoric acid or a precursor ofan inorganic phosphoric acid.

11. A lithographic printing plate precursor comprising a substrate ofany of embodiments 1 to 10 and at least one radiation-sensitiveimageable layer disposed over the substrate without any intermediatepost-treatment layer on the substrate, the radiation-sensitive imageablelayer comprising a radiation absorber.

12. The precursor of embodiment 11 that is a negative-workinglithographic printing plate precursor having a negative-workingradiation-sensitive imageable layer comprising a free radicallypolymerizable compound, the radiation absorber, and a compound togenerate free radicals upon irradiation.

13. The precursor of embodiment 11 or 12 that is a negative-workinglithographic printing plate precursor having a negative-working,infrared radiation-sensitive imageable layer comprising a free radicallypolymerizable compound, an infrared radiation absorber, and a compoundto generate free radicals upon irradiation.

14. A method of preparing a lithographic printing plate comprising:

imagewise exposing the lithographic printing plate precursor of any ofembodiments 11 to 13 to provide an exposed precursor having exposed andnon-exposed regions in the radiation-sensitive imageable layer, and

processing the exposed precursor to remove either the non-exposedregions or the exposed regions to provide a lithographic printing plate.

15. The method of embodiment 14 wherein the processing further removesthe hydrophilic layer in either the non-exposed regions or the exposedregions that are removed.

16. The method of embodiment 14 or 15 wherein the lithographic printingplate precursor is a positive-working lithographic printing plateprecursor, and processing the exposed precursor is carried out off-pressto remove the exposed regions to provide a lithographic printing plateusing an alkaline processing solution.

17. The method of embodiment 14 or 15 wherein the lithographic printingplate precursor is a negative-working lithographic printing plateprecursor, and processing of the exposed precursor is carried outoff-press using water or an alkaline processing solution to remove thenon-exposed regions to provide a lithographic printing plate.

18. A lithographic printing plate obtained by the method of any ofembodiments 14 to 17 wherein the lithographic printing plate comprises asubstrate having thereon either exposed portions or non-exposed portionsof a radiation-sensitive imageable layer.

19. A method for preparing an aluminum-containing article, comprising:

treating a grained and sulfuric acid anodized aluminum-containingsupport with an alkaline or acidic pore-widening solution to providecolumnar pores in the outer surface so that the diameter of the columnarpores at their outermost surface is at least 90% of the average diameterof the columnar pores, to provide a substrate, and

without post-treating the substrate, forming a hydrophilic layerdirectly on the substrate from a hydrophilic layer formulation, thehydrophilic layer comprising a non-crosslinked hydrophilic polymerhaving carboxylic acid side chains, the non-crosslinked hydrophilicpolymer being applied to a dry coverage of at least 0.001 g/m² and up toand including 0.4 g/m² to form the substrate of any of embodiments 1 to10.

20. The method of embodiment 19 comprising treating the grained andsulfuric acid anodized aluminum-containing support to remove at least 10weight % and up to and including 80 weight % of the original aluminumoxide from sulfuric acid anodization using the alkaline or acidicpore-widening solution.

21. The method of embodiment 19 or 20 further comprising forming anegative-working radiation-sensitive imageable layer directly on thehydrophilic layer.

22. The method of any of embodiments 19 to 21 comprising treating thegrained and sulfuric acid anodized aluminum-containing support with thealkaline or acidic pore-widening solution that comprises sodiumhydroxide, potassium hydroxide, sulfuric acid, hydrochloric acid, nitricacid, or phosphoric acid, or mixtures of the acids or mixtures of thehydroxides.

23. The method of any of embodiments 19 to 22 comprising treating thegrained and sulfuric acid anodized aluminum-containing support with thealkaline or acidic widening solution at a temperature of at least 20° C.for at least 3 seconds for pore widening to provide columnar poreshaving an average diameter of at least 20 nm and up to and including 40nm.

24. The method of any of embodiments 19 to 23 wherein the hydrophiliclayer formulation consists essentially of a non-crosslinked hydrophilicpolymer and an inorganic phosphoric acid.

The following Examples are provided to illustrate the practice of thisinvention and are not meant to be limiting in any manner. The followingmaterials were used in the preparation and evaluation of the Examples:

On-Press Developable Lithographic Printing Plate Precursors:

G2 Support without Hydrophilic Layer:

An electrochemically grained, sulfuric acid-anodized aluminum supporthaving no hydrophilic layer was prepared (R_(a)=0.4 μm, OD=0.3, andoxide weight of 2.7 g/m²). R_(a) is the average roughness of the supportsurface and OD is the optical density of the support. Both parametersare measured using known measuring techniques and apparatus.

PW1 Support:

The noted G2 support was treated with a 0.3 weight % sodium hydroxidesolution for 17 seconds at 40° C. for pore widening. The resultingsubstrate was washed with de-ionized water and dried at 100° C. for 60seconds.

PW2 Support:

The noted G2 support was treated with an alkaline solution of 0.25weight % of sodium hydroxide and 1.06 weight % of sodium carbonate for17 seconds at 40° C. The resulting substrate was washed with de-ionizedwater and dried at 100° C. for 60 seconds.

PW3 Support:

The noted G2 support was further treated with an alkaline solution of0.28 weight % of sodium hydroxide for 17 seconds at 40° C. The resultingsubstrate was washed with de-ionized water and dried at 100° C. for 60seconds.

PW4 Support:

The noted G2 support was further treated with an acid solution of 1.0weight % of hydrogen chloride for 17 seconds at 45° C. The resultingsubstrate was washed with de-ionized water and dried at 100° C. for 60seconds.

The following TABLE I summarizes the various supports:

TABLE I Component D1* D2** D1/D2 G2 support  8.14 nm PW1 support 29.79nm 27.84 nm 107% PW2 support 29.25 nm PW3 support 25.74 nm PW4 support23.12 nm *D1 is the diameter of the columnar pores at their outermostsurface **D2 is the average diameter of the columnar pores

D1 was measured by following procedure:

A microphotograph of the support was prepared using a field emissionscanning electron microscope S-4500 (Hitachi Ltd, of Tokyo Japan).

Fifty pores on each microphotograph were picked randomly and the lengthof the X axis and Y axis was measured for each pore.

The average diameter (D1) of each pore was determined for eachmicrophotograph by averaging the 50 X axis and Y axis results.

D2 was measured by following procedure:

A cross-section microphotograph of the support was prepared using thefield emission scanning electron microscope S-4500.

Ten pores on each cross-section microphotograph were picked randomly,and the diameter inside each pore was measured at 9 points (Z axis fromthe substrate surface). These observing points inside the pore weredetermined randomly.

The average diameter of the columnar pores was determined from theaverage of these 9 diameters.

D2 was determined by the diameter average of evaluations of the 10pores.

Substrates were coated with a hydrophilic layer and dried as describedbelow in TABLE IV using the formulations described in TABLES II and III(parts by dry weight in 0.8% aqueous solutions) below to provide a drycoating weight of 0.22 g/m² for further evaluation. The hydrophiliclayer drying conditions were 120° C. for 50 seconds.

TABLE II Component* SE1** SE2** SE3** SE4** Kemguard ™ 5041 72 0 94 47AC-10S 0 43 0 0 YS-100 0 29 0 0 Phosphoric acid 22 22 0 0 NT-20 6 6 6 6PVA-103 0 0 0 47 PVA-203 0 0 0 0 Luvitec ™ K30 0 0 0 0 *Componentsdefined below

TABLE III Component* SC1** SC2** SC3** SC4** SC5 Kemguard ™ 5041 0 0 0 00 AC-10S 72 0 0 0 0 YS-100 0 72 0 0 0 Phosphoric acid 22 22 0 0 0 NT-206 6 6 6 6 PVA-103 0 0 94 0 0 PVA-203 0 0 0 94 0 Luvitec ™ K30 0 0 0 0 94*Components defined below

Kemguard™ 5041 is an aqueous solution (50 weight %) of poly(acrylicacid) that was obtained from Charkit Chemical Company (Connecticut).

AC-10S is an aqueous solution (45 weight %) of poly(acrylic acid) thatwas obtained Toa Gosei (Tokyo, Japan).

YS-100 is an aqueous solution (40 weight %) of poly(acrylic acid, sodiumsalt that was obtained from Nippon Shokubai (Tokyo, Japan).

NT-20 is poly(oxyethylene)alkyl ether that was obtained from NipponNyukazi (Tokyo, Japan).

Luvitec™ K30 is poly(vinyl pyrrolidone) that was obtained from BASFJapan (Tokyo, Japan).

PVA-103 is a poly(vinyl alcohol) (98 mol % OH groups) that was obtainedfrom Kuraray (Tokyo, Japan).

PVA-203 is a poly(vinyl alcohol) (88 mol % OH groups) that was obtainedfrom Kuraray (Tokyo, Japan).

Silicate Interlayer Treatment:

An electrochemically grained, sulfuric acid-anodized aluminum-containingsupport was immersed in a 4 weight % sodium silicate aqueous solutionfor 17 seconds at 60° C. The silicate-treated support was then washedwith de-ionized water and dried at 100° C. for 60 seconds.

Poly(Vinyl Phosphonic Acid) (PVPA) Interlayer Treatment:

An electrochemically grained, sulfuric acid-anodized aluminum-containingsupport was immersed in a 0.4 weight % of PVPA aqueous solution for 17seconds at 60° C. The PVPA-treated support was washed with de-ionizedwater and dried at 100° C. for 60 seconds.

Silicate Interlayer & Hydrophilic Layer Treatment:

The silicate-treated support was immersed in a 4% sodium silicateaqueous solution for 17 seconds at 60° C. The SE1 hydrophilic layerformulation described above in TABLE II was applied to and dried on thissupport to provide a dry coating weight of 0.15 g/m² at 120° C. for 50seconds, except for BC-12 that had a dry coating weight of 0.5 g/m²after drying at 120° C. for 50 seconds.

TABLE IV Silicate + Hydrophilic Hydrophilic Substrate Support LayerSilicate PVPA Layer B-1 PW1 SE1 None None None B-2 PW2 SE1 None NoneNone B-3 PW1 SE2 None None None B-4 PW1 SE3 None None None B-5 PW1 SE4None None None B-6 PW3 SE1 None None None B-7 PW4 SE1 None None NoneBC-1 PW1 None None None None BC-2 PW1 None Yes None None BC-3 PW1 NoneNone Yes None BC-4 PW1 None None None Yes BC-5 G2 None None None NoneBC-6 G2 SE1 None None None BC-7 PW1 SC1 None None None BC-8 PW1 SC2 NoneNone None BC-9 PW1 SC3 None None None BC-10 PW1 SC4 None None None BC-11PW1 SC5 None None None BC-12 PW1 SE1 None None None

Onto the various substrates were coated the negative-working imageablelayer formulations E1, E2, E3, E4, E5, and C1 as described below inTABLE V. Each formulation was applied as an 8 weight % solution insolvent mixture of n-propanol:propylene glycol methyl ether:methyl ethylketone:water (weight ratio of 4:1:4:1) and dried at 110° C. to provide adry coating weight of 1.2 g/m².

TABLE V (% solids) Component E1 E2 E3 E4 E5 C1 Polymer 1 12% 0 12% 12% 044%  Polymer 2 32% 25%  32% 32% 40%  0 A-1  5% 0 0 0 5% 5% A-2 0 5%  5%0 0 0 A-3 0 0 0  5% 0 0 Borate A 5% 5%  5%  5% 5% 5% Irgacure ® 250 0 5%0 0 0 0 initiator Oligomer 1 15% 0 15% 15% 17%  12%  Oligomer 2 25% 45% 25% 25% 27%  23%  3-MT 0 2% 0 0 0 0 Irganox ® 0 1% 0 0 0 0 1035 Klucel E0 5% 0 0 0 0 Naxan ® 0 1% 0 0 0 0 ABL Leuco dye  5% 5%  5%  5% 5% 5%Phosmer PE 0 0 0 0 0 1% Byk ® 337  1% 1%  1%  1% 1% 1%

The structure of Polymer 1 is represented by the following formula:

Polymer 2 was a 25 weight % dispersion of an acrylonitrile/polyethyleneglycol methyl ether methacrylate/styrene copolymer in an 80/20 mixtureof n-propanol/water, and was prepared like Polymer A described in U.S.Pat. No. 7,592,128 (Huang et al., bottom of Column 27).

A-1 had the following formula:

A-2 had the following formula:

A-3 had the following formula:

Borate A had the following formula:

Irgacure® 250 is a 75 weight % solution of iodonium,(4-methoxyphenyl)[4-(2-methylpropyl)phenyl]-, hexafluorophosphate inpropylene carbonate that is available from Ciba Specialty Chemicals(Tarrytown, N.Y.).

Oligomer 1 is a urethane acrylate as a 80 weight % solution in2-butanone and is prepared by reacting DESMODUR® N100 (an aliphaticpolyisocyanate resin based on hexamethylene diisocyanate from BayerCorp., Milford, Conn.) with hydroxyethyl acrylate and pentaerythritoltriacrylate.

Oligomer 2 is ethoxylated 4 pentaerythritol tetraacrylate that isavailable as SR-494 from Sartomer Japan (Yokohama, Japan).

3-MT is 3-mercapto-1,2,4-triazole that is available from Tokyo Kasei(Tokyo, Japan).

Irganox® 1035 is thio diethylenebis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) that is availablefrom Ciba Specialty Chemicals (Tarrytown, N.Y.).

Klucel E is hydroxypropylcellulose that is available from Hercules(Wilmington, Del.).

Naxan® PLUS ABL is an alkyl Naphthalene sulfonate, sodium salt that isavailable from NEASE Performance Chemicals.

The leuco dye is represented by the following formula:

Phosmer PE is represented by the following formula and is available fromUni-chemical:

Byk® 337 is a modified dimethyl polysiloxane copolymer that is availablefrom Byk Chemie (Wallingford, Conn.).

Printing Plate Precursors:

The detail of each printing plate precursor is shown in the followingTABLE VI and the imaging and evaluation results are shown in TABLE VIIbelow.

TABLE VI Printing Plate Imageable Precursor Substrate Layer Invention 1B-1 E1 ″ 2 B-2 E1 ″ 3 B-3 E1 ″ 4 B-1 E2 ″ 5 B-1 E3 ″ 6 B-1 E4 ″ 7 B-1 E5″ 8 B-4 E1 ″ 9 B-5 E1 ″ 10 B-6 E1 ″ 11 B-7 E1 Comparison 1 BC-3 E1 ″ 2BC-1 E1 ″ 3 BC-3 C1 ″ 4 BC-2 E1 ″ 5 BC-4 E1 ″ 6 BC-2 C1 ″ 7 BC-5 E1 ″ 8BC-6 E1 ″ 9 BC-5 C1 ″ 10 BC-7 E1 ″ 11 BC-8 E1 ″ 12 B-1 C1 ″ 13 BC-9 E1 ″14 BC-10 E1 ″ 15 BC-11 E1 ″ 16 BC-12 E1

TABLE VII Printing BG BG Imaging Plate (start, 0 (after 2,000 Energy DOPof DOP of Precursor impressions) impressions) (mJ/cm²) LOR Fresh PlateAged Plate Blocking Invention 1 OK OK 150 A A B A 2 OK OK 150 A A B A 3OK OK 150 A A A A 4 OK OK 200 B A B B 5 OK OK 150 A A B A 6 OK OK 150 AA B A 7 OK OK 150 A B C A 8 OK OK 150 A A B A 9 OK OK 150 A B C A 10 OKOK 150 A A B A 11 OK OK 150 A B B A Comparison 1 OK OK 150 C A D A 2 NGNA NA NA NA NA NA 3 OK OK 250 C A E E 4 NG NA NA NA NA NA NA 5 NG NA NANA NA NA NA 6 OK OK 300 D A E E 7 NG NA NA NA NA NA NA 8 OK OK 150 D A CB 9 NG NA NA NA NA NA E 10 OK OK 150 A B D A 11 OK NG 150 A A B A 12 OKOK 300 C A B E 13 OK OK 150 A D E A 14 OK OK 150 A C E A 15 NG NA NA NANA NA NA 16 OK OK 150 D A B A

In TABLE V, “BG” refers to the background scumming at press start (0impressions) and after 2,000 printed impressions. IR speed was decidedby the imaging power point that showed same ink density of 1×1 checkerflag and 2×2 checker flag of Magnus 800 imagesetter (Eastman KodakCompany, 830 nm imaging wavelength, 210 rpm drum speed, 13W currentsetting of the laser diode at 150 mJ/cm² imaging power). “LOR” refers tothe “press life” of the lithographic printing plate (an indication ofdurability). “DOP” refers to the developing speed of the lithographicprinting plate on the printing press. The difference of DOP(fresh) andDOP(aged) indicated the aging property of each test plate. The“Blocking” property indicates the degree of tackiness for each test.“NA” means not applicable or not available. “NG” refers to a “no good”result. The evaluations “A”, “B”, “C”, “D”, and “E” represent a range ofvery good (A) to very poor (E).

The LOR data were obtained using a Sprint-26 printing press (KomoriCorporation, Tokyo) at a speed of 9,000 rpm. The fountain solution was amixture of 10% isopropanol and 1% K-701 (DIC, Tokyo) in water. Theprinter's blanket was 57400 that is available from Kinyo-sha (Tokyo). OKtopcoat paper matte N grade paper (Oji Paper, Tokyo) was used forprinted impressions, and the lithographic printing ink was FINE INK KPGMagenta N grade ink (DIC, Tokyo).

The BG and DOP data were obtained using a Roland 200 printing press (ManRoland Japan, Saitama Toda, Japan) that was run at 9,000 rpm. Thefountain solution was a mixture 1% isopropanol and 1% NA-108W (DIC,Tokyo) in water. The printer's blanket was 57400 noted above. OK topcoatpaper matte N grade paper (noted above) was used for printedimpressions, and the lithographic printing ink was Fusion G Magenta Ngrade ink (DIC, Tokyo).

The “blocking” property was determined by cutting a lithographicprinting plate precursor into samples of 10.16 cm by 12.7 cm size, andplacing a pressure on them of 6.24 kg_(f)/cm² with TP-40 interleavingpaper (Tokyushu-seishi, Tokyo) between the samples for five days, andthen evaluating the degree of blocking from the interleaving paperbetween the samples.

All of the lithographic printing plate precursors of this inventioncomprised a substrate that had been treated for pore widening and wascoated with a non-radiation sensitive hydrophilic layer comprising anon-crosslinked hydrophilic polymer having carboxylic acid side chains.Each of these invention precursors showed excellent printingperformance. The lithographic printing plate precursors having no porewidening of their substrates, Comparison Examples 7 and 8, showed verypoor performance. The improved effect observed with the Inventionprecursors was achieved from the improved adhesion of the pore-widenedsupport and the improved on-press developability provided by the noncrosslinked hydrophilic layer in the substrate.

However, even if the substrate was treated for pore widening, if thenon-crosslinked hydrophilic layer contained no carboxylic acid sidegroups, poorer press life (LOR) was observed, as with ComparisonExamples 1 and 3.

In Comparison Examples 4, 5, and 6, poorer releasability of theradiation-sensitive imageable layer was observed because the silicateinterlayer in the substrate exhibits poor release of the non-imagedregions of the imageable layer during on-press printing. Most of thenon-imaged imageable layer remained on the pore-widened substrate inComparison Examples 4-6.

PVA103 and PVA203 are water-soluble polymers that do not have carboxylicside groups and when they were used as the non-radiation sensitivehydrophilic layer, the precursors exhibited relatively poor DOP(Comparison Examples 13 and 14) because of their slower water-solublespeed. On the other hand, the use of poly(vinyl pyrrolidone) providedpoor results because that polymer is soluble in the imageable layerformulation solvent, and caused increased background because theimageable layer components migrated to the hydrophilic layer on thesubstrate.

No hydrophilic layer was present under the imageable layer in ComparisonExamples 2 and 9, and the imaged lithographic printing plate precursorscould not be developed on press.

Comparison Example 11 showed good on-press DOP at the start of printing,but the background of the plate showed the ink scumming gradually asprinting continued because YS-100 was neutralized PAA and was easy todissolve in the fountain solution during lithographic printing. Thus,the hydrophilic layer using in Comparison Example 11 was removed duringprinting on the press and ink scumming was observed after 2,000impressions.

On the other hand, Comparison Example 10 exhibited lower DOP on freshand unacceptably poor DOP with an aged printing plate. This means thatsome PAA cause slow dissolving speed into a fountain solution, resultingin a slower DOP was seen. Invention Example 3 comprised a mixture of PAAand neutralized PAA in the non crosslinked hydrophilic polymer in thesubstrate. PAA and neutralized PAA can exchange their cations in theSE02 solution of TABLE II very quickly to obtain a partially neutralizedpolymer that provides good balance of BG after 2,000 printingimpressions property and a desired DOP for aged printing plates.

Comparison Example 16 showed good on-press developability at thebeginning of the printing cycle, but the imaged printing layer wasdestroyed quickly because the hydrophilic layer was too thick.

Positive-Working Lithographic Printing Plate Precursors:

Synthesis of Resin 1:

In a 10 liter flask equipped with a stirrer, a capacitor, and a droppingdevice, 2,990 g of dimethylacetamide were charged and heated to 90° C.Then, 740.5 g of phenyl maleimide, 1,001 g of methacrylamide, 368 g ofmethacrylic acid, 643 g of acrylonitrile, 203.6 g of Phosmer M(manufactured by Uni-Chemical Co, Ltd.), 222.5 g of styrene, 10.6 g ofAIBN free radical initiator, and 16 g of n-dodecylmercaptan weredissolved in 2,670 g of dimethylacetamide. The resulting solution wasadded dropwise to a reactor over 2 hours. After completion of thedropwise addition, 5.3 g of AIBN were added to the solution and itstemperature was raised to 100° C., followed by stirring for 4 hours.During stirring, the reaction was continued by adding 5.3 g of AIBNevery hour. After the completion of the reaction, heating was stopped,and the resulting reaction solution was cooled to room temperature. Thereaction solution was poured into 50 liters of water and the resultingprecipitate was collected by filtration under reduced pressure, washedonce with water, and collected by filtering again under reducedpressure. The precipitate was vacuum-dried at 50° C. for 24 hours toobtain Resin 1 in an amount of 2,873 g (yield of 90%).

Lower Layer Coating Formulation:

A lower layer coating formulation was prepared using the compounds shownin TABLE VIII below.

TABLE VIII Grams Methyl ethyl ketone 47.28 Propylene glycol monomethylether 28.37 γ-Butyrolactone 9.46 Water 9.46 Resin 1 3.95 Cyanine IR dyeA (see below) 0.50 Cyanine IR dye B (see below) 0.40 D11 (see below)0.10 Paintad 19 (manufactured by Dow Corning) 0.05Upper Layer Coating Formulation:

An upper layer coating formulation was prepared using the compoundsshown in TABLE IX below.

TABLE IX Grams Methyl isobutyl ketone 66.32 Acetone 19.00 Propyleneglycol monomethyl ether acetate 9.50 SMA resin* (average molecularweight: 200) 4.93 Victoria Pure Blue BOH-M 0.02 Paintad 19 0.05 *SMAresin is a copolymer derived from styrene and maleic anhydride (molarratio of 1:1).

Preparation of Lithographic Printing Plate Precursor:

The lower layer coating formulation of TABLE VIII was applied to each ofthe inventive substrates described below in TABLE X using a bar coaterand then dried at 100° C. for 2 minutes to provide a dry coating weightof 1.5 g/m². On each dried lower layer, the upper layer coatingformulation of TABLE IX was applied using a bar coater and then dried at100° C. for 2 minutes to provide a dry coating weight of 0.5 g/m².

TABLE X Printing Plate Substrates of Precursor TABLE VI Invention 12 B-1″ 13 B-6 Comparison 17 BC-1 ″ 18 BC-2Preparation of Developing Solution:

A developing solution was prepared using the compounds shown in TABLE XIbelow to have a pH of 11.5 and conductivity of 1.2 mS/cm.

TABLE XI Grams Deionized water 700 Monoethanolamine 10 Diethanolamine 30Pellex NBL (manufactured by Kao Corporation) 200 Benzyl alcohol 60Preparation of Lithographic Printing Plate:

Each of the two-layered lithographic printing plate precursors obtainedas described above was exposed at 150 mJ/cm² using a PTR4300imagesetter, developed with a developing solution (prepared by dilutingthe developing solution shown in TABLE XI with water five times) at 30°C. for 15 seconds using an automatic processor (P-940X, manufactured byEastman Kodak Company), and then finished using finishing gum PF2(manufactured by Eastman Kodak Company) to obtain lithographic printingplates.

Off-Press Developable Negative-working Lithographic Printing PlatePrecursors:

A free radical photosensitive imageable layer coating formulation wasprepared using the compounds shown below in TABLE XII.

TABLE XII Compound Grams Propylene glycol methyl ether 30.664 Methylethyl ketone 59.664 Polymer A 2.02 Polymer B 0.132 ACA 230AA 3.813 IRDye A 0.187 DPHA 2.847 Dye B 0.264 MDP 0.075 Initiator A 0.536 P3B 0.038

Polymer A is a copolymer derived from methacrylic acid, allylmethacrylate, and methyl methacrylate.

Polymer B has the structure described below and was provided as a 25weight % solution in methyl isobutyl ketone.

IR dye A has the following structure:

DPHA is di-pentaerythritol hexaacrylate that is available from NIPPONKAYAKU (Tokyo).

Dye B is a triphenylmethane having the following structure:

MDP shown below and is available from SUMITOMO Chemical (Tokyo).

P3B is described below and is available from SHOWA DENKO (Tokyo).

Borate A has the following structure:

ACA230AA is an alkaline soluble acrylic polymer having ethylenicallyunsaturated pendant groups (53% solids) that is available from DAICELchemical (Osaka, Japan).

A protective overcoat coating formulation was prepared using thecompounds shown in TABLE XIII below.

TABLE XIII Compound Grams PVA-203 1.956 Luvitec ™ K30 0.652 Newcol 23050.086 Newcol 2320 0.174 Water 96.963

PVA-203 and Luvitec™ K30 are already described above.

Newcol 2305 is poly(oxyethylene)alkyl ether that was obtained fromNippon Nyukazi (Tokyo, Japan).

Newcol 2320 is poly(oxyethylene)alkyl ether that was obtained fromNippon Nyukazi (Tokyo, Japan).

Preparation of Lithographic Printing Plate Precursor:

The imageable layer coating formulation described above was applied ontoeach of the inventive substrates described below in TABLE XIV using abar coater and then dried at 100° C. for 2 minutes to provide a drycoating weight of 1.2 g/m². The protective overcoat coating formulationwas applied over each dried imageable layer using a bar coater and thendried at 100° C. for 2 minutes to provide a dry coating weight of 0.5g/m².

TABLE XIV Printing Plate Substrates of Precursor TABLE VI Invention 14B-1 ″ 15 B-6 Comparison 19 BC-1 ″ 20 BC-2Preparation of Lithographic Printing Plate:

Each of the lithographic printing plate precursors described above wasexposed at 90 mJ/cm² using a PTR4300 imagesetter, developed using adeveloper (prepared by diluting TND-1 from Kodak-Japan, Tokyo with waterby 3.5 times) at 30° C. for 12 seconds using an automatic processor(PK-1310 news, manufactured by Eastman Kodak Company), and then finishedusing finishing gum NF-3 (manufactured by Eastman Kodak Company) dilutedwith water one time to obtain a lithographic printing plate.

Printing Press Test:

In TABLE XV below, “BG” refers to the background scumming at press start(0 impressions) and after 2,000 printed impressions. “LOR” refers to the“press life” of the lithographic printing plate (an indication ofdurability). “NA” means not applicable or not available. “NG” refers toa “no good” result. The evaluations “A”, “B”, “C”, “D”, and “E”represent a range of very good (A) to very poor (E).

The LOR data were obtained using a Sprint-26 printing press (KomoriCorporation, Tokyo) at a speed of 9,000 rpm. The fountain solution was amixture of 10% isopropanol and 1% K-701 (DIC, Tokyo) in water. Theprinter's blanket was 57400 that is available from Kinyo-sha (Tokyo). OKtopcoat paper matte N grade paper (Oji Paper, Tokyo) was used forprinted impressions, and the lithographic printing ink was FINE INK KPGMagenta N grade ink (DIC, Tokyo).

The BG data were obtained using a Roland 200 printing press (Man RolandJapan, Saitama Toda, Japan) that was run at 9,000 rpm. The fountainsolution was a mixture of 1% isopropanol and 1% NA-108W (DIC, Tokyo) inwater. The printer's blanket was 57400 noted above. OK topcoat papermatte N grade paper (noted above) was used for printed impressions, andthe lithographic printing ink was Fusion G Magenta N grade ink (DIC,Tokyo).

TABLE XV Printing BG BG Plate (start, 0 (after 2,000 Precursorimpressions) impressions) LOR Invention 12 OK OK A ″ 13 OK OK B ″ 14 OKOK A ″ 15 OK OK B Comparison 17 NG NG NA ″ 18 OK NG C ″ 19 NG NG NA ″ 20OK NG D

Both the off-press developable negative-working lithographic printingplate precursors and the positive-working lithographic printing plateprecursors described above that were prepared using eight the B-1 or B-6substrate needed developing process showed excellent LOR without anybackground scumming(BG) during the start of printing and after 2,000impressions. On the other hand, the lithographic printing plateprecursors prepared using the BC-1 substrate showed severe backgroundscumming because of the lack of the hydrophilic layer, and they couldnot be evaluated. The lithographic printing plate prepared using theBC-2 substrate also showed poorer background scumming after 2,000impressions and poorer LOR due to its cross-linked polymer that had nocarboxylic acid side chains.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

The invention claimed is:
 1. A lithographic printing plate precursorcomprising a substrate and at least one radiation-sensitive imageablelayer disposed over the substrate, the radiation-sensitive imageablelayer comprising a radiation absorber, the substrate comprising agrained and sulfuric acid anodized aluminum-containing support, whichsupport has also been treated with an alkaline or acidic pore-wideningsolution to provide its outer surface with columnar pores so that theaverage diameter of the columnar pores at their outermost surface is atleast 90% of the average diameter of the columnar pores and is at least20 nm and up to and including 40 nm, the substrate further comprising ahydrophilic layer that is directly disposed on and that is at leastpartially within the columnar pores on the grained, sulfuric acidanodized and treated aluminum-containing support, the hydrophilic layercomprising a non-crosslinked hydrophilic polymer having carboxylic acidside chains, wherein the substrate does not comprise post-treatmentcoatings of poly(vinyl phosphonic acid), vinyl phosphonic acidcopolymers, silicates, dextrin, calcium zirconium fluoride,hexafluorosilicate, or a phosphate solution containing an inorganicfluoride.
 2. The precursor of claim 1 wherein the non-crosslinkedhydrophilic polymer is present at a dry coverage of at least 0.001 g/m²and up to and including 0.4 g/m².
 3. The precursor of claim 1 that is anegative-working lithographic printing plate precursor having anegative-working radiation-sensitive imageable layer comprising a freeradically polymerizable compound, the radiation absorber, and a compoundto generate free radicals upon irradiation.
 4. The precursor of claim 1that is a negative-working lithographic printing plate precursor havinga negative-working, infrared radiation-sensitive imageable layercomprising a free radically polymerizable compound, an infraredradiation absorber, and a compound to generate free radicals uponirradiation.
 5. The precursor of claim 1 wherein the non-crosslinkedhydrophilic polymer has carboxylic acid side chains that are neutralizedto a degree of at least 1 mol % and up to and including 60 mol %.
 6. Theprecursor of claim 1 wherein the non-crosslinked hydrophilic polymer ispresent at a dry coverage of at least 0.01 g/m² and up to and including0.3 g/m².
 7. The precursor of claim 1 wherein the grained and sulfuricacid anodized and treated aluminum-containing support has beenelectrochemically grained.
 8. The precursor of claim 1 wherein thehydrophilic layer is a non-radiation-sensitive hydrophilic layer.
 9. Amethod of preparing a lithographic printing plate comprising: imagewiseexposing the lithographic printing plate precursor of claim 1 to providean exposed precursor having exposed and non-exposed regions in theradiation-sensitive imageable layer, and processing the exposedprecursor to remove either the non-exposed regions or the exposedregions to provide a lithographic printing plate.
 10. The method ofclaim 9 wherein the processing further removes the hydrophilic layerthat is disposed directly on the substrate and under theradiation-sensitive imageable layer, in either the non-exposed regionsor the exposed regions that are removed.
 11. The method of claim 9wherein the lithographic printing plate precursor is a negative-workinglithographic printing plate precursor, and processing of the exposedprecursor is carried out off press using water or an alkaline processingsolution to remove the non-exposed regions to provide a lithographicprinting plate.
 12. A method of preparing a lithographic printing platecomprising: imagewise exposing the lithographic printing plate precursorof claim 1 that is a positive-working lithographic printing plateprecursor, to provide an exposed precursor having exposed andnon-exposed regions in the radiation-sensitive imageable layer, andprocessing the exposed precursor off-press using an alkaline processingsolution to remove the exposed regions to provide a lithographicprinting plate.
 13. A lithographic printing plate precursor comprising asubstrate and at least one radiation-sensitive imageable layer disposedover the substrate, the radiation-sensitive imageable layer comprising aradiation absorber, the substrate comprising a grained and sulfuric acidanodized aluminum-containing support, which support has also beentreated with an alkaline or acidic pore-widening solution to provide itsouter surface with columnar pores so that the average diameter of thecolumnar pores at their outermost surface is at least 90% of the averagediameter of the columnar pores and is at least 20 nm and up to andincluding 40 nm, the substrate further comprising a hydrophilic layerthat is disposed directly on and that is at least partially within thecolumnar pores on the grained, sulfuric acid anodized and treatedaluminum-containing support, the hydrophilic layer comprising anon-crosslinked hydrophilic polymer having carboxylic acid side chains,and an inorganic phosphoric acid or a precursor of an inorganicphosphoric acid, wherein the substrate does not comprise post-treatmentcoatings of polyvinyl phosphonic acid), vinyl phosphonic acidcopolymers, silicates, dextrin, calcium zirconium fluoride,hexafluorosilicate, or a phosphate solution containing an inorganicfluoride.